​​WASHINGTON, Aug 16 (Reuters): U.S. President Donald Trump on Sunday instructed the Pentagon to "substantially reduce" 10 days of joint military exercises with South Korea as they were about to get underway, citing the cost of the drills and Seoul's refusal to take part in actions against Iran.

Hours before exercises were scheduled to begin, Trump said on his Truth Social site that although it was too late to cancel the drills entirely, he was "not happy" that the U.S. had previously agreed to participate and highlighted his "very good relationship" with North Korean leader Kim Jong Un.

"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 annual Ulchi Freedom Shield joint military exercises are scheduled to run from August 17 to 27, with about 18,000 South Korean military ⁠personnel participating. The drills are expected to include operations to counter drones, disrupt GPS signals and cyberattacks to adapt to North Korea's evolving capabilities, officials said last week.

South Korea's Joint Chiefs of Staff told Reuters that the drills started on Monday as scheduled, but declined comment on Trump's comments. The country's presidential office and defense and foreign ministries did not immediately respond on a public holiday in Seoul.

A Pentagon spokesperson referred questions on the matter to the White House, which did not immediately respond to a request for more information on next steps for the drills.

Photo from Reuters