WASHINGTON (AP) — President Donald Trump directed the Pentagon on Sunday to reduce the scope of planned joint military exercises with South Korea, citing Seoul’s refusal to assist the United States in efforts to denuclearize Iran.

Trump said in a social media post that the exercises, scheduled to start this week, are expensive and “send a signal that is totally inappropriate and hostile” to North Korea. He also said North Korea “has been unthreatening and respectful” during his time in the White House.

“Therefore, and based on the fact that it is too late to cancel, I have instructed Secretary of War, Pete Hegseth, to substantially reduce the Joint Military Exercises!” Trump wrote. He also said he had recently asked South Korean President to support U.S. efforts to denuclearize Iran, “and they said, ‘No thanks!’”

The 11-day military exercises, involving 18,000 South Korean troops, were intended to strengthen the allies’ preparedness for potential threats from North Korea.

North Korea issued a warning Friday, threatening unspecified stern measures against the United States and South Korea. Pyongyang described the military exercises as “a rehearsal for an aggressive war” and accused the drills of contributing to heightened instability across the region.

Such warnings are common from North Korea before major U.S.-South Korean military exercises. Experts say Pyongyang has frequently pointed to the drills as justification for expanding its weapons testing, strengthening its military capabilities and rallying domestic support behind leader Kim Jong Un.

Under the original plans, U.S. and South Korean forces were expected to rehearse combined operations under complicated battlefield conditions. The exercises were to include a live-fire drill testing joint precision targeting and maneuver capabilities, a wet-gap crossing operation and the distribution of military equipment that had been positioned in advance, according to the U.S. military.