Washington/Seoul: US President Donald Trump has instructed the Pentagon to “substantially reduce” joint military exercises with South Korea, citing the cost of the drills, tensions with North Korea and Seoul’s refusal to participate in US military action against Iran.

The announcement came just hours before the annual Ulchi Freedom Shield exercises were due to begin.

In a post on his Truth Social platform, Trump said he was unhappy that the United States had agreed to take part in the military drills and argued they sent the wrong message to North Korea.

“These exercises are not only costly… but send a signal that is totally inappropriate and hostile, to a Country that, as long as Donald J. Trump has been President, has been unthreatening and respectful,” Trump wrote.

The drills are scheduled to run until August 27 and involve approximately 18,000 South Korean military personnel.

South Korea’s Joint Chiefs of Staff told Reuters the exercises began as scheduled on Monday but declined to comment on Trump’s remarks.

Trump’s comments highlighted his continued emphasis on diplomacy with North Korean leader Kim Jong Un, with whom he held three summits during his previous presidency.

The US president has long advocated scaling back military exercises with South Korea, while also pressing Seoul to contribute more towards the costs of hosting approximately 28,500 US troops stationed on the Korean Peninsula.

North Korea routinely condemns the drills as preparations for an invasion.

The latest controversy comes after Pyongyang launched two ballistic missiles since August 6, including a missile fired toward the Sea of Japan last week.

Jenny Town, director of the Stimson Center’s 38 North programme, said the move could be linked to Trump’s renewed interest in diplomacy with North Korea.

“This decision may be part of a larger effort to create a diplomatic opportunity with Pyongyang, as Trump has consistently wanted since coming back to office.”

Trump also linked his decision to South Korea’s refusal to participate in efforts related to the conflict involving Iran.

In his social media post, Trump said he had recently asked South Korean President Lee Jae Myung whether South Korea wished to join efforts aimed at the denuclearisation of Iran.

“They said, ‘No thanks!'” Trump wrote.

The US-South Korea alliance has experienced periodic disagreements over defence cost-sharing and military commitments despite remaining one of Washington’s key security partnerships in Asia.

Military experts note that recent exercises have already been scaled back compared with previous years, relying more heavily on simulations rather than live-fire training.

Victor Cha, president of the Geopolitics and Foreign Policy Department at the Center for Strategic and International Studies, suggested Trump may be seeking leverage with Pyongyang at a time when North Korea’s ties with Russia have deepened.

“The other way to look at this is that Trump wants to engage Kim as a way to impede the Russia-North Korea ties,” Cha said.

US officials have previously warned that North Korean troops and missile programmes have gained valuable experience through cooperation with Russia during the war in Ukraine.

The decision also comes amid broader economic differences between Washington and Seoul.

A former US official told Reuters that Trump has been frustrated by what he views as a lack of progress from the South Korean government on economic commitments and investment agreements.

Last year, the two countries reached a trade agreement aimed at reducing US tariffs on automobiles in exchange for South Korean investment commitments worth $350 billion, though details of the investment plan have yet to be announced publicly.

The allies have also faced disputes involving US-listed e-commerce company Coupang, which is under investigation in South Korea over a significant data breach.