US President Donald Trump said "great progress" was being made in the push to persuade North Korea to end its nuclear program after agreeing Thursday to talks with his counterpart Kim Jong Un.
"Meeting being planned!" Trump said on Twitter after the White House confirmed that the US leader had agreed to meet Kim.
"Kim Jong Un talked about denuclearization with the South Korean Representatives, not just a freeze. Also, no missile testing by North Korea during this period of time," Trump said after a top South Korea official announced the talks would be held by May.
"Great progress being made but sanctions will remain until an agreement is reached."
However President Trump's Director of National Intelligence, Dan Coats, told Congress he was "quite skeptical" and Vice President Mike Pence said the US position towards North Korea would not change "until we see credible, verifiable, and concrete steps toward denuclearisation".
It comes after South Korea delegates reportedly hand-delivered a letter from North Korean leader Kim Jong-un to the White House.
'Committed to denuclearisationi'
South Korea's National Security Adviser Chung Eui-yong told reporters Mr Kim also said he was committed to denuclearisation, adding: "Kim pledged that North Korea would refrain any further nuclear missile tests."
"He expressed his eagerness to meet with Donald Trump as soon as possible," Mr Chung told reporters at the White House.
"President Trump appreciated the briefing and said he would meet Kim Jong-un by May to achieve permanent denuclearisation.
Mr Chung reaffirmed South Korea, the United States and its partners were committed to denuclearisation and a peaceful resolution.
White House national security adviser H.R. McMaster and other senior aides were briefed on Thursday (local time) by South Korean officials on their talks with North Korea this week.
US network CNN is reporting South Korean officials hand-delivered a letter from North Korean leader Kim Jong-un to the White House, citing a diplomatic source, according to Reuters.
Mr Chung is visiting Washington to brief US allies about his recent landmark talks with North Korean leader Kim Jong-un in Pyongyang.
South Korea announced on Tuesday the North had stated there was "no reason" to hold on to its nuclear weapons "if military threats towards the North are cleared and the security of its regime is guaranteed".
The North is open to "frank" talks with the United States on denuclearisation and would suspend missile and nuclear tests while dialogue was underway, Mr Chung said after returning from a meeting in Pyongyang with Kim.
Japan welcomes talks
Japan's prime minister welcomed the surprise announcement of a summit.
"I highly appreciate North Korea's change that it will begin talks on the premise of denuclearisation," Shinzo Abe said, adding that he planned to visit the United States to meet Trump "as early as April".
Japan has been cautious about a recent Olympics-driven rapprochement on the Korean peninsula, with Mr Abe warning on Thursday that "talks for the sake of talks are meaningless".
But he sounded a positive note on the planned Trump-Kim summit, hailing it as "the achievement of cooperation between... Japan, the US, and South Korea to maintain great pressure".
"We will keep putting maximum pressure (on North Korea) until North Korea takes concrete actions toward denuclearisation in a manner that is complete, verifiable and irreversible."
Mr Abe said he had spoken to Mr Trump this morning and "agreed that I'd like to visit the US and have a summit with him as early as April".
Japan, a close US ally in the region, is in the direct firing line of North Korean missiles and saw two fly over its territory in 2017, sparking outrage and lifting tensions to fever pitch.
South Korean envoys are expected to visit Japan next week to brief Mr Abe on the latest developments in the fast-moving apparent detente.
- with Reuters, AFP, and additional reporting from Louise Cheer