SEOUL, South Korea — South Korea’s president said Tuesday a solid alliance with the United States underpins national security, after U.S. President Donald Trump’s abrupt order to “substantially reduce” joint military exercises left many many South Koreans baffled and concerned.

Trump made the surprise announcement in a social media post just before U.S. and South Korean soldiers began Monday’s annual Ulchi Freedom Shield exercises, which are largely designed to sharpen readiness against North Korean threats.

Trump cited what he said was a good relationship with North Korean leader Kim Jong Un and South Korea’s refusal to join the U.S. war against Iran.

Trump’s move was apparently taken without consultations with South Korea and meant to reach out to Kim, deepening concerns about the reliability of the U.S.-South Korean alliance forged in the turmoil of the 1950-53 Korean War.

A weakening of the U.S. defense commitment could shake South Korea’s national security as it has no nuclear weapons and is under the U.S. “nuclear umbrella” protection, which guarantees a devastating American response in the event of an attack on its ally by nuclear-armed North Korea. The U.S. has about 28,500 troops in South Korea.

Confidence in the U.S. has already eroded among many South Koreans because of Trump’s tariff war and last year’s immigration raid in the U.S. state of Georgia that led to the detention of hundreds of South Korean workers.

Trump’s announcement “reveals the stark reality of a faltering Korea-U.S. alliance, fueling public anxiety,” South Korea’s Hankook Ilbo newspaper said in an editorial Tuesday. “It’s absurd that the U.S. appears to treat North Korea more respectfully than its ally South Korea.”

South Korean leader calls for solid US alliance

In a regular Cabinet meeting, South Korean President Lee Jae Myung stressed the importance of a firm military alliance with the U.S., saying that “national security will be further strengthened when the alliance is solid.”