President Donald Trump is directing the Pentagon to reduce the scale of U.S. participation in joint military exercises with South Korea, citing the expense of the drills, the South’s unwillingness to back U.S. efforts on Iran, and his relationship with North Korean leader Kim Jong Un.

The decision came as the annual Ulchi Freedom Shield exercise was due to begin Aug. 17. South Korea said the exercise would go ahead as planned, meaning the drills were not outright cancelled.

Trump said on Truth Social that he was unhappy with the long-time U.S. commitment to the exercises. They were expensive and sent what he called an inappropriate and hostile signal to North Korea, he said.

Trump also discussed his relationship with Kim, calling it “a very good relationship” with the North Korean leader. He posted an older photo of the two leaders from their 2019 meeting at the inter-Korean border less than 24 hours before announcing the change.

Separately, the president said he asked South Korean President Lee Jae-myung whether Seoul wanted to join U.S. efforts to "denuclearise" Iran. 'South Korea said no,' Trump said. The White House has not released any additional information about the call. It’s critical to differentiate between what Trump has claimed and what has been independently confirmed.

Timing of the announcement was important because the annual exercise had already been planned. The 11-day exercise will involve about 18,000 South Korean troops and be roughly similar in scale to those in previous years, according to South Korean and U.S. military officials.

The exercises are meant to enhance the allies’ capability to counter an array of security threats. Forces Korea describes Ulchi Freedom Shield as a combined exercise involving live, virtual, constructive and field training across multiple domains of military operations.

The exercise comes as fresh concerns arise over North Korea’s military capabilities. Pyongyang has continued to develop its nuclear and missile programmes and has recently resumed ballistic missile testing. North Korea has also provided military support to Russia in its war against Ukraine, providing its forces with battlefield experience that U.S. and South Korean officials have said is relevant to alliance planning.

North Korea has long accused the United States and South Korea of using their military drills to prepare for an invasion. Its criticism of the drills has been usually accompanied by threats or weapons tests.

The latest U.S. move also places Seoul in a tight position. South Korea’s defence strategy is premised on the U.S. military presence and the bilateral alliance, which it is heavily dependent on, but successive U.S. administrations have pressured Seoul to assume a larger share of the costs of the alliance.

Trump had previously suspended large U.S.-South Korea military exercises in 2018 as part of his first-term diplomacy with Kim. He said at the time the drills were provocative and discussed how much they cost. The exercises were then modified again during the Covid-19 pandemic.

Trump’s latest move comes after he has expressed renewed interest in engaging Kim. His first term in office saw three high-profile meetings with the North Korean leader, but no denuclearisation deal survived. The Hanoi summit in 2019 unravelled the talks.

The decision thus presents competing priorities for Washington: maintaining military readiness with a key Asian ally while trying to create conditions for renewed engagement with Pyongyang.

For Seoul, the key question is how much the U.S. participation cut will affect the military value of the exercise and whether it signals a broader shift in Washington’s approach to the alliance.