WASHINGTON — Defense Secretary Jim Mattis says the United States and South Korea will scale back a major military exercise next spring to avoid setting back diplomacy over North Korea’s nuclear weapons.

Mattis told reporters at the Pentagon on Wednesday that the exercise, which is called Foal Eagle and is conducted each spring in South Korea, will be “reduced in scope.” The decision had not previously been announced.

He did not provide details, but the decision is an extension of efforts by Washington and Seoul to encourage progress in stalled negotiations over the North’s nuclear program.

In Mattis’s words, the exercise next spring will be scaled back to a level that will “not be harmful to diplomacy.” North Korea strongly objects to large-scale U.S.-South Korean military exercises.