The United States has canceled a joint amphibious landing exercise with South Korean forces that was set for next month, citing resource constraints driven by the war in Iran, the South Korean military announced Monday.

The U.S. Marine Corps had notified its South Korean counterpart in June that Middle East operational demands would prevent the deployment of forces for the biennial exercise known as Ssangyong, or “Twin Dragons,” the South Korean Marine Corps said on Monday. The U.S. military in Korea did not immediately comment on the announcement.

The move marked the second joint military drill with South Korea to be canceled or downsized during President Trump’s second term. The decision has intensified doubts over Washington’s commitment to maintaining a credible deterrent on the Korean Peninsula and ​its capacity to manage concurrent global conflicts, as U.S. weapons stockpiles have fallen to troubling levels.

Ssangyong is one of the highest-profile joint exercises that the allies have conducted for decades. In a typical iteration, more than 10,000 Marines from both countries storm a sandy beach on the southeastern coast of South Korea, supported by columns of amphibious vehicles and fleets of military aircraft. North Korea has routinely condemned the drill as a rehearsal for invasion.

While Ssangyong was previously shelved during Mr. Trump’s first term​ —​ when he dismissed major exercises as “provocative” and too expensive amid his personal diplomacy with the North Korean leader Kim Jong-un​ —​ it was revived in 2023.

However, Mr. Trump recently renewed his criticism of the drills, labeling them “insulting” to Mr. Kim. Earlier this month, he abruptly ordered the Pentagon to curtail the Ulchi Freedom Shield, shortening the 11-day annual exercise to just five days.

“The U.S. and South Korean Marine Corps are continuing close consultations regarding the future resumption” of Ssangyong, Han Seung-jeon, a South Korean Marine Corps spokesman, said on Monday.

Beyond financial concerns, Mr. Trump has questioned why his country should support joint military drills when South Korea has declined to participate in the conflict with Iran. The war has significantly strained U.S. military resources, depleting critical munitions stockpiles and forcing a realignment of assets from Asia to the Middle East.

Mr. Trump also appears eager to pivot from the Middle East conflict toward renewed diplomatic engagement with Mr. Kim, with whom he once said he “fell in love.” While halting drills successfully incentivized Mr. Kim to negotiate​ during Mr. Trump’s first term, North Korea dismissed this month’s scaling down of Ulchi Freedom Shield as “unworthy of comment.”