SEOUL/WASHINGTON: US President Donald Trump said he was prepared to meet North Korea’s Kim Jong Un in what would be the first face-to-face encounter between the two countries’ leaders and could mark a breakthrough in a standoff over the North’s nuclear weapons.

Kim had “committed to denuclearization” and to suspending nuclear and missile tests, South Korea’s National Security Office head Chung Eui-yong told reporters at the White House on Thursday after briefing Trump on a meeting South Korean officials held with Kim earlier this week.

Kim and Trump had engaged in an increasingly bellicose exchange of insults over the North’s nuclear and missile programs, which it pursues in defiance of UN Security Council resolutions, before an easing of tension coinciding with last month’s Winter Olympics in the South.

“A meeting is being planned,” Trump posted on Twitter after speaking to Chung, setting up what would be his biggest foreign policy gamble since taking office in January 2017.

Chung said Trump had agreed to meet by May in response to Kim’s invitation. A senior U.S. official said later it could happen “in a matter of a couple of months, with the exact timing and place still to be determined”.

Both Russia and China, who joined years of on-again, off-again “six-party” talks, along with the United States, the two Koreas and Japan, aimed at ending the standoff, welcomed the new, positive signals after months of deteriorating relations between North Korea and the United States.

Trump had derided the North Korean leader as a “maniac”, referred to him as “little rocket man” and threatened in a speech to the United Nations last year to “totally destroy” Kim’s country of 26 million people if it attacked the United States or one of its allies.

Kim responded by calling the U.S. president a “mentally deranged U.S. dotard”.

South Korean President Moon Jae-In, who led the pursuit of detente with North Korea during his country’s hosting of the Winter Olympics, said the summit would set a course for denuclearization, according to a presidential spokesman. Trump had agreed to meet Kim without any preconditions, another South Korean official said.

Asian stock markets rose on the news, with Japan's Nikkei ending up 0.5 percent and South Korean stocks more than 1 percent higher. The dollar also rose against the safe-haven Japanese yen.

“It’s good news, no doubt,” said Hong Chun-Uk, chief economist at Kiwoom Securities in Seoul. “But this will likely prove to be only a short-lived factor unless more and stronger actions follow.”

Trump had previously said he was willing to meet Kim under the right circumstances but had indicated the time was not right for such talks. He mocked U.S. Secretary of State Rex Tillerson in October for “wasting his time” trying to talk to North Korea.

Tillerson said earlier on Thursday during a visit to Africa that, although “talks about talks” might be possible with Pyongyang, denuclearization negotiations were likely a long way off.

“Kim Jong Un talked about denuclearization with the South Korean Representatives, not just a freeze,” Trump said on Twitter on Thursday night. “Also, no missile testing by North Korea during this period of time. Great progress being made but sanctions will remain until an agreement is reached.”

A meeting between Kim and Trump, whose exchange of insults had raised fear of war, would be a major turnaround after a year in which North Korea has carried out a battery of tests aimed at developing a nuclear-tipped missile capable of hitting the U.S. mainland.

Trump’s aides have been wary of North Korea’s diplomatic overtures because of its history of reneging on international commitments and the failure of efforts on disarmament by previous U.S. administrations.

South Koreans responded positively to the news, with online comments congratulating Moon for laying the groundwork for the Trump-Kim talks. Some even suggested Moon should receive the Nobel Peace prize, although scepticism over previous failed talks remained.

North and South Korea, where the United Sates stations 28,500 troops, are technically still at war after their 1950-53 conflict ended in a ceasefire, not a truce.