Vigilant Ace is an annual exercise.
The Pentagon provided no details about the size of Vigilant Ace, exercises which have been undertaken under different names for a decade.
Japanese Defense Minister Takeshi Iwaya and his United States and South Korean counterparts, James Mattis and Jeong Kyeongdoo, participated in trilateral consultations on the sidelines of the meeting of the Association of Southeast Asian Nations (ASEAN) defense ministers, according to the NHK broadcaster. It was announced later in the night.
"Both ministers are committed to modifying training exercises to ensure the readiness of our forces". She said the need for future exercises would continue to be evaluated.More news: Apple CEO Tim Cook urges Bloomberg to retract spy chip story
Defense ministers from the US and South Korea "are committed to modifying training exercises to ensure the readiness of our forces". It has been conducted for nine years.
Mattis was in Singapore for a meeting of Asian defence ministers. The two countries have agreed not to hold joint military exercises, a move they hope will encourage North Korea to engage in meaningful dialogue.
United States and South Korean forces have been training together for years, and routinely rehearse everything from beach landings to an invasion from the North, or even "decapitation" strikes targeting the North Korean regime.
According to the agreement signed after the third summit between South Korean President Moon Jae-in and North Korean leader Kim Jong-un last month in Pyongyang, the two militaries began 20-day demining operations on October 1.
Senior US military officials have said they have ways of adjusting to limited suspensions of exercises with South Korea but that at some point the lack of exercising the procedures involved in commanding and controlling combat forces will erode their preparedness for war.More news: Jordan wants Israel to return lands leased under 1994 peace deal
"I would say it was a prudent risk if we're willing to make the effort to change the relationship with (North Korea)", Ten Robert Abrams told members of the Senate Armed Services Committee then.
In August, Mattis insisted to Pentagon reporters that the range of training exercises have "never been turned off".
Trump has regularly made statements in recent weeks suggesting all US military exercises with South Korea had been suspended. "So there are ongoing exercises all the time on the peninsula".
Mattis has said the "good faith effort" of suspending that exercise was not open-ended and that he wanted to wait and see how future negotiations with North Korea progress before making a decision about future large-scale exercises, particularly the Foal Eagle exercise scheduled for the spring.More news: Jimmy Carter Says Brett Kavanaugh 'Unfit' To Serve As Supreme Court Justice