WASHINGTON—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, U.S. defence secretary Jim Mattis said Wednesday.

Mattis told reporters at the Pentagon that the exercise, known as Foal Eagle and conducted each spring in South Korea to keep ground, air, naval and special operations forces prepared for combat, will be “reduced in scope.”

“Foal Eagle is being reorganized a bit to keep it at a level that will not be harmful to diplomacy,” he said.

North Korea has vigorously protested these and other large-scale annual military exercises, calling them provocations and a dress rehearsal for an invasion. The U.S. and South Korea insist the maneuvers are purely defensive.

In October, the U.S. and South Korea cancelled a major exercise, Vigilant Ace, that was to be conducted in December, and after U.S. President Donald Trump’s June summit in Singapore with North Korean leader Kim Jong Un, the U.S. cancelled a major summertime exercise, Ulchi Freedom Guardian, which Trump derided as wasteful and provocative.

Mattis did not provide details about how Foal Eagle will be reorganized and toned down, but the decision is an extension of efforts by Washington and Seoul to encourage progress in stalled negotiations over the North’s nuclear program.