President Donald Trump ordered the Pentagon to substantially reduce annual joint military exercises with South Korea, citing the country’s refusal to support the U.S. war against Iran.

Trump said the exercises are costly and send an inappropriate and hostile signal to North Korea, pointing to his relationship with North Korean leader Kim Jong Un.

The president said he recently asked South Korea to join the U.S. in the “denuclearization” of Iran, but the country declined.

The decision represents a shift from the administration’s recent praise of South Korea for increasing defense spending and taking greater responsibility for security on the Korean Peninsula, NPR has reported.

The 11-day exercises involving about 18,000 South Korean troops were intended to strengthen military readiness against potential threats from North Korea.