Trump tweeted that he never talked about this issue with Kim during their recent summit, adding that he had decided to downgrade those exercises long ago because of the tremendous cost that cannot be reimbursed.

"The reason I do not want military drills with South Korea is to save hundreds of millions of dollars for the US for which we are not reimbursed," Trump said in a previous tweet on Sunday. "Also, reducing tensions with North Korea at this time is a good thing!"

The Pentagon on Saturday announced in a statement that Washington and Seoul had decided to "conclude" the Key Resolve and Foal Eagle series of military exercises, which Pyongyang has denounced as a dress rehearsal for northward invasion.

The United States and South Korea will maintain military readiness through newly designed Command Post exercises and revised field training programs, according to the statement.

The adaption of the joint training program, the statement said, reflected "our desire to reduce tension and support our diplomatic efforts to achieve complete denuclearization of the Korean Peninsula in a final, fully verified manner."

The move came right after Trump's second meeting with Kim, held in the Vietnamese capital Hanoi on Feb 27-28, without reaching an agreement.

Nevertheless, the White House said the two leaders had "very good and constructive meetings" and discussed various ways to "advance denuclearization and economic driven concepts."

About 28,500 US troops are stationed in South Korea, vestigial of the 1950-53 Korean War that ended with an armistice.