The Defense Department is changing up a major exercise it holds annually with South Korea, Defense Secretary Jim Mattis said Wednesday at the Pentagon.

"[Exercise Foal Eagle is] being reorganized a bit to keep it at a level that will not be harmful to diplomacy," Mattis said.

He did not disclose whether that means a reduction in forces participating, normally about 30,000 U.S. troops, or combining it with another exercise held at a different time of year.

Foal Eagle is a combined ground, air, naval and special operations field exercise, "designed in the spirit of the U.S.-South Korean mutual defense treaty of 1953," according to the Pentagon.

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More than 3,000 U.S.-based troops deploy each year for the drill and join up with the 28,000 service members stationed on the peninsula.

Mattis said no other major changes are planned to scheduled exercises.

In a statement released following Mattis' remarks Wednesday, Pentagon officials reiterated that Mattis and Republic of Korea Minister of National Defense Jeong Kyeongdoo had jointly agreed that exercises should be conducted "in a manner that complements diplomatic efforts to achieve North Korea's denuclearization" while sustaining readiness.

"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," Marine Lt. Col. Christopher Logan, a Pentagon spokesman, said in a statement. "We continue to look at multiple aspects of future exercises to include their size and scope."

In August, Mattis said there were no major cancellations planned for future exercises after President Donald Trump expressed interest in scaling back and spending less on joint military exercises with South Korea.

"We have no plans at this time to suspend any more exercises," Mattis said at the time. "We will work very closely with [Secretary of State Mike Pompeo] and what he needs done, we will certainly do to reinforce his effort. But at this time, there is no discussion about further suspensions."

The Pentagon had indefinitely suspended larger-scale summer exercises with South Korea, most notably Ulchi Freedom Guardian, at the Trump administration's request following the president's meeting with North Korea's leader Kim Jong Un in Singapore.

Mattis reiterated in August what the Defense Department had announced in June following the Singapore Summit: The U.S. had suspended larger exercises -- what Trump at the time characterized as "war games" -- but smaller training efforts with South Korean counterparts would remain on the calendar.

"There are ongoing exercises all the time on the [Korean] peninsula," he said.

Mattis said the smaller exercises have not been publicized to avoid misinterpretation by North Korea, which may view them as a "break in faith" following the June negotiations.

U.S. and South Korean forces earlier in the year postponed two exercises, Foal Eagle and Key Resolve, in a pledge to downsize military training until the Winter Olympics in South Korea had concluded.

The month-long exercises kicked off in April and were expected to include 12,000 U.S. troops and nearly 300,000 South Korean forces.

Weeks before the games, the U.S. had held the wing-level exercise Beverly Herd -- which officials at the time characterized as "non-major" -- with counterparts at Osan Air Base.

-- Oriana Pawlyk can be reached at oriana.pawlyk@military.com. Follow her on Twitter at @Oriana0214.