Defense Secretary Jim Mattis has “indefinitely suspended” joint military exercises with South Korea as part of the agreement to get North Korea to denuclearize, the Pentagon announced late Friday.

The exercises were called “provocative” by President Donald Trump, who also questioned their cost-effectiveness, and he agreed with North Korean leader Kim Jong-Un to cancel them as part of an agreement reached in Singapore that could lead to North Korea getting rid of its nuclear weapons.

However, the exercises have been an integral part of improving joint operability with South Korea’s military, and they are considered a key part of the U.S. commitment to protect Seoul from a potential attack from the North.

The next exercise, Ulchi Freedom Guardian, was scheduled for August and involved more than 17,500 U.S. service members.

“To support implementing the outcomes of the Singapore Summit, and in coordination with our Republic of Korea ally, Secretary Mattis has indefinitely suspended select exercises,” Pentagon press secretary Dana White said in a statement. “This includes suspending Freedom Guardian along with two Korean Marine Exchange Program training exercises scheduled to occur in the next three months.”

The Pentagon did not say if the suspension would be carried through to its next major exercises, planned for spring 2019.

The spring exercise, Foal Eagle, was pushed back this year so it wouldn’t clash with the Winter Olympics. An air portion of that exercise, Max Thunder, irked the North Korean leader to the point that he canceled a pre-summit talk with South Korean president Moon Jae-In.

“In support of upcoming diplomatic negotiations led by Secretary Pompeo, additional decisions will depend upon the DPRK continuing to have productive negotiations in good faith,” White said.