Prosecutors in Spain targeted the Venezuelan oilman Alejandro Betancourt in one money laundering inquiry. Swiss authorities investigated him in another. Both countries requested his extradition from Britain, where Mr. Betancourt lives in a 14-bedroom country estate, and British authorities arrested him less than a year ago, barring him from traveling abroad.

All of it hardly mattered.

As part of the Trump administration’s takeover of Venezuela’s oil industry, the United States is forming an extraordinary partnership with Mr. Betancourt. Under the arrangement, the Pentagon could seek to take a large stake in his company, a deal that defies easy comparison in recent American history, oil analysts say.

That would make Mr. Betancourt the main partner of the Trump administration as it pushes not just to control the sale of Venezuela’s oil, but to own a chunk of it directly. And it would place Mr. Betancourt at the core of Venezuela’s deepening transformation from a sovereign nation into essentially a vassal state of the United States.

Secretary of State Marco Rubio brought up Mr. Betancourt in a White House meeting in the spring. He had decided that Mr. Betancourt could be a viable partner for the United States because he had experience forging oil deals in Venezuela and increasing production there, said a person familiar with U.S. efforts to support Mr. Betancourt.

That meant Mr. Betancourt would need to be able to travel freely. Officials from the State Department and the Justice Department intervened in the Swiss investigation by reaching out to Swiss counterparts to persuade them not to go forward with the extradition, according to people familiar with the matter.

They also asked Britain’s government to ease travel restrictions on Mr. Betancourt, the people said, allowing him to travel to Venezuela and to the United States to meet with Trump administration officials. The British government was reluctant but eventually agreed to the request.

Under the deal with the Trump administration, a financing office within the Pentagon plans to partner with Mr. Betancourt’s oil company, North American Blue Energy Partners, or NABEP, which is being granted 100-year concessions to operate 17 oil fields in Venezuela.

Mr. Betancourt does not own the fields, but the concessions give him the exclusive rights to exploit them — and they are potentially enormous. In all, these oil fields have estimated reserves of 65 billion barrels, nearly as much as all the proven reserves in the United States.

“The United States has wreaked havoc on us” with this deal, said Rafael Ramírez, a former Venezuelan energy minister. He called the unusual arrangement with Mr. Betancourt “grotesque” and “unsustainable in the long run” because it was done in secret with an authoritarian government many Venezuelans view as illegitimate, echoing criticism across Venezuela’s normally polarized political spectrum.

Sara Chouraqui, a spokeswoman for Mr. Betancourt and the general counsel for his oil company, rejected the criticism.

“To Alejandro, this isn’t political,” Ms. Chouraqui said. “The fact that he is now in a position to revitalize the country’s long-dormant economic potential is in itself a win, not for any one political party, but for all of Venezuela.”

This article is based on interviews with oil executives, current and former U.S. officials, and former Venezuelan officials, some of whom spoke on condition of anonymity to discuss sensitive diplomacy.

In settling on Mr. Betancourt, the Trump administration opted against partnering directly with a U.S. oil giant like Chevron, which has had extensive operations in Venezuela for decades, or Petroleos de Venezuela, the country’s state-owned oil company.

The deal with Mr. Betancourt holds some parallels with the transition from state socialism to market capitalism in post-Soviet Russia, when the West worked with newly anointed oligarchs to gain access to Russian oil reserves.

“It’s actually eerily similar,” said Francisco Rodríguez, a Venezuelan economist. In both cases, Mr. Rodríguez said, weak governments handed over key parts of their oil industries to well-connected figures. In Russia, he noted, these oligarchs grew immensely rich while often supporting authoritarian rule.

In response to a request for comment on U.S. efforts to press Switzerland and Britain to lower the legal pressure on Mr. Betancourt, the State Department cited a briefing on Tuesday in which a top U.S. official told reporters that the administration had found “no pending legal problems in the United States.” The ongoing legal cases had largely originated from U.S. prosecutors’ efforts to look into Mr. Betancourt’s dealings about a decade ago, the official said.

The White House had no comment, while the Justice Department and the British Embassy in Washington did not respond to requests for comment. The Washington Post reported earlier on some details of U.S. efforts to help Mr. Betancourt with his legal challenges.

Explaining the deal, Mr. Rubio told a Venezuelan journalist this week that the partnership with Mr. Betancourt was “going to be professionalized” and will “operate under laws that will apply to it so that the money is never used improperly.”

President Trump has promoted the deal as a way to lower gasoline prices and replenish U.S. strategic oil reserves, though the effort could take years, at best, and there are questions about whether the Pentagon has the legal authority to pursue the deal.

Mr. Betancourt has a long history operating in the shadowy world of secretive oil deals, regime power struggles and multiple financial crime investigations.

But until news of the deal emerged in recent days, Mr. Betancourt, 46, born into an upper-crust family that traces its lineage to a 19th-century Venezuelan president, was largely known for mastering the art of landing deals with Venezuela’s authoritarian leaders while still in his 20s.

Reaping a bonanza from no-bid contracts with Venezuela’s government, he plowed that money into trophy real estate around the world, including a penthouse in Manhattan’s Olympic Tower and a castle in Spain with extensive hunting grounds, as he shifted into new ventures, from African banks to pumping Venezuelan oil.

While the deal with the Trump administration is unorthodox, there is strong reasoning for this new approach, according to Venezuelan oil experts.

Franco Sampieri, the director of the Petroleum Chamber of Zulia, the oil-producing state in western Venezuela, said he believed the deal would bring many direct and indirect jobs to the region.

“We are 30 years behind,” Mr. Sampieri said, emphasizing that Zulia desperately needed such an initiative to help resuscitate the industry.

Petróleos de Venezuela is a hollowed-out shell of what it once was, hobbled by mismanagement and corruption, dimming its allure as a potential partner. Mr. Betancourt also has a reputation, however marred by allegations of impropriety it may be, of getting business done and raising oil production in Venezuela.

The Trump administration may also have a kind of leverage over Mr. Betancourt that it couldn’t exert over a major U.S. oil company, especially after his arrest in Britain last November in connection to international money laundering inquiries.

If Mr. Betancourt doesn’t toe the line, the Trump administration could reverse course and press foreign legal authorities to revisit allegations, or push the Justice Department to reactivate its investigation into a U.S. money laundering case in Miami. In that case, Mr. Betancourt was identified, albeit not by name, as an unindicted co-conspirator, according to a person familiar with the case.

The help Mr. Betancourt has gotten from the U.S. government to evade further scrutiny — instead of it treating him as a potential witness in other corruption inquiries, or even as an unindicted co-conspirator — has shocked former Justice Department officials, the person familiar with the Miami investigation said.

Mr. Betancourt has recently become close to Mauricio Claver-Carone, the powerful political operator who is close to Mr. Rubio, according to two people with knowledge of their relationship. Mr. Claver-Carone has been instrumental in shaping Venezuela policy despite holding no formal role in the Trump administration.

Mr. Betancourt comes from a privileged background. His father was a cardiologist and pianist, and his mother a jewelry designer. He attended an elite private high school in Caracas before studying business at Boston’s Suffolk University.

When he returned to Venezuela, high oil prices were setting off an economic boom. Hugo Chávez’s revolution was in full swing as the Venezuelan leader sought to use oil revenues to consolidate power, fund antipoverty projects and lift Venezuela’s profile on the world stage.

But amid Mr. Chávez’s expropriations and anti-American rhetoric, there were also opportunities to make a great deal of money in a short amount of time. Mr. Betancourt cut his teeth selling turbines, which allowed him to develop ties with government officials.

Leveraging those contacts, Mr. Betancourt got into the business of building power plants at a time when Venezuela was experiencing electricity shortages. Despite having little experience in the power generation sector, Mr. Chávez’s government awarded him an array of no-bid contracts.

José Aguilar, an independent Venezuelan energy auditor who often coordinated his work with Venezuelan civic transparency organizations, found that Mr. Betancourt’s company overbilled state entities by more than $800 million for the power plants, often by tacking on massive markup fees.

Separately, prosecutors in Europe and the United States investigated claims that executives at Mr. Betancourt’s company paid tens of millions of dollars in bribes to secure the contracts.

Mr. Betancourt was not charged as a result of the multiple investigations into these activities, and Ms. Chouraqui, his spokeswoman, said he had never been charged with a crime in any jurisdiction.

Even so, Mr. Aguilar called the U.S. government’s decision to partner with Mr. Betancourt “shameful.”

All of Mr. Betancourt’s early deals laid the foundation for a rapid accumulation of wealth. But they also exposed him to scorn from many Venezuelans who viewed him as a traitor for dealing with a government that was jailing dissidents, purging the civil service of critics and nationalizing parts of the economy.

Mr. Betancourt made his foray into Venezuela’s oil industry in 2011 by acquiring a minority stake in Petrozamora, a state-controlled producer operating oil fields in Lake Maracaibo.

Coordinating with other minority owners from Russia, Mr. Betancourt held on to his stake in Petrozamora until 2022, when one of the Venezuelan government’s periodic purges pushed him out of the company at the behest of Tareck El Aissami, the oil minister at the time and a rival of Delcy Rodríguez, then the vice president.

But Mr. Al Aissami’s purge was short lived, and served as the catalyst for his own arrest in 2024 on corruption charges.

After his stake in Petrozamora was expropriated, Mr. Betancourt navigated the fallout by aligning with the regime faction led by Ms. Rodríguez, who is now Venezuela’s president, and her brother, Jorge Rodríguez, the head of the National Assembly.

He regained his stake in Petrozamora in 2024 through NABEP, a newly created company registered in Barbados. The company helped execute a rapid operational turnaround, lifting production from 20,000 barrels a day to about 200,000.

In doing so, NABEP emerged as the second-largest private oil company in Venezuela, coming within reach of Chevron’s production of about 280,000 barrels a day.

As the Trump administration tries to ramp up Venezuela’s overall oil output, that positioned Mr. Betancourt not only as a key interlocutor between Washington and Caracas, but someone poised to amass even greater wealth and power as a partner of the U.S. government.

Isayen Herrera contributed reporting.