South Korea and the United States will scale back a joint military exercise next spring to facilitate negotiations over North Korea's nuclear weapons program, US Defense Secretary Jim Mattis said Wednesday.

Mattis told reporters at the Pentagon that the Foal Eagle exercise will be "reduced in scope," the AFP reported.

It will be the fifth joint exercise to be adjusted as a concession to the North following its promise to dismantle its nuclear and ballistic missile programs.

"Foal Eagle is being reorganized a bit to keep it at a level that will not be harmful to diplomacy," the news agency quoted Mattis as saying.

US President Donald Trump and North Korean leader Kim Jong-un agreed at their historic Singapore summit in June to work toward "complete" denuclearization of the Korean Peninsula.

But negotiations between the sides have since stalled.

Trump said after the summit that the "provocative" and "expensive" war games with South Korea would be stopped while negotiations were under way.

North Korea regards the exercises as invasion rehearsals against the regime despite assurances from Seoul and Washington they are defensive in nature.

Foal Exercise is a major joint exercise held every spring. The other two large-scale drills are the Ulchi Freedom Guardian and Key Resolve.

Since the summer, the allies have suspended the Ulchi Freedom Guardian, two marine exercises and the Vigilant Ace air drills.

The Pentagon said that other exercises are also up for review.

"We continue to look at multiple aspects of future exercises to include their size and scope," Lt. Col. Chris Logan, a Pentagon spokesperson, said in a statement released after Mattis' remarks.

He said the secretary and South Korean Defense Minister Jeong Kyeong-doo agreed during talks last month to conduct military activities, including exercises, in a way that complements diplomatic efforts to achieve the North's denuclearization and sustains the readiness of the allied forces.

"The Secretary and Minister agreed to continue the close review of all large-scale combined military exercises, and to make coordinated decisions based on the advice of our military commanders," Logan said. (Yonhap)