United States President Donald Trump said Sunday it was his idea to suspend joint military exercises by South Korea and the US to foster favorable conditions for denuclearization talks with North Korea, adding that the military drills will immediately start back up if the talks collapse.

"Holding back the 'war games' during the negotiations was my request because they are very expensive and set a bad light during a good faith negotiation," the US president wrote in a Twitter message, also calling the drills "quite provocative."

Trump first floated the idea of suspending the war games with South Korea in a press conference that followed his historic summit with North Korean leader Kim Jong-un, held in Singapore on Tuesday.

His remarks prompted concerns in South Korea where many, especially conservatives, believe the joint exercises are a key deterrence to North Korean aggression.

Seoul and Washington have long insisted their joint military exercises here are strictly defensive in nature.

South Korean President Moon Jae-in has also acknowledged a need to at least temporarily suspend the joint drills as long as North Korea is in denuclearization talks in good faith.

"Most of all, it is important to understand that removing military tensions and hostile relations between the two countries by establishing a new North Korea-US relationship and opening new relations in the future is the only way to completely denuclearize North Korea and bring peace to the Korean Peninsula," Moon said Thursday in a National Security Council meeting.

In his Twitter message, the US president said the joint military exercises "can start up immediately if talks break down, which I hope will not happen."

Trump made similar remarks on Friday, telling reporters at the White House that it was his offer to halt the drills.

"I call them 'war games.' I hated them from the day I came in ... We pay millions and millions of dollars for planes, and all of this," he said at the time.

In separate tweets Sunday, Trump claimed that he got "so much for peace in the world," and "more is being added in finals."

"The denuclearization deal with North Korea is being praised and celebrated all over Asia. They are so happy!" he wrote, bemoaning that in his own country, some people would "rather see this historic deal fail than give Trump a win."

Trump and Kim signed a joint statement following their meeting that reaffirmed the North's commitment to work towards "complete denuclearization of the Korean Peninsula." Trump in return committed to provide "security guarantees" to the regime. (Yonhap)