By Steve Holland and Christine Kim
WASHINGTON/SEOUL (Reuters) - The White House said on Monday it fully expected an unprecedented meeting between U.S. President Donald Trump and North Korean leader Kim Jong Un to take place, if North Korea stuck to its promises, even though Pyongyang has yet to comment publicly on the possibility of a summit.
A South Korean delegation that visited North Korea last week said North Korean leader Kim Jong Un expressed a wish to meet Trump and South Korea's president to discuss denuclearisation. North Korean media have reported the South Korean visit, but no details of the talks.
Asked if the North Korean silence meant there was a chance the meeting between Trump and Kim would not take place, White House spokeswoman Sarah Sanders said: “We fully expect that it will.
"The offer was made and we’ve accepted. North Korea made several promises and we hope that they would stick to those promises and if so the meeting will go on as planned," she told a regular briefing.
Earlier, South Korea said North Korea's silence on summits with both the United States and South Korea was probably because of caution in preparing for the meetings, while U.S. Secretary of State Rex Tillerson said Washington expected to hear directly from Pyongyang.
"We have not seen nor received an official response from the North Korean regime regarding the North Korea-U.S. summit," said Baik Tae-hyun, spokesman for South Korea's Unification ministry.
"I feel they're approaching this matter with caution and they need time to organise their stance."
Tillerson said several steps would be necessary to agree on the location and scope of the talks, adding later that a "neutral" site would be needed.
"It's very early stages. We've not heard anything directly back from North Korea but we expect to hear something directly from them," he said during a visit to Nigeria.
In an unexpected move last week, Trump agreed to hold a first-ever meeting with Kim, which South Korea said would take place by the end of May after a North-South summit in April.
News of possible talks has been a dramatic turnaround from fears of war over North Korea's development of nuclear-tipped missiles capable of hitting the United States.
Trump made the announcement after the head of a South Korean delegation that met Kim last week said the North Korean leader had committed to denuclearisation and pledged to refrain from nuclear and missile tests.
Asked in a Fox News interview due to air on Monday evening whether there was a real possibility of North Korea denuclearising, U.S. Vice President Mike Pence said: "We'll see, as the president often says."
But Pence called Kim's offers to cease missile and nuclear testing while not objecting to U.S.-South Korean military exercises "a remarkable step forward" and a result of Trump's tough approach.
"He's marshalled unprecedented economic and diplomatic pressure on the regime in North Korea and this breakthrough - and we hope it is a breakthrough - is a result of the strong leadership the president has provided on the world stage," Pence said.
Kim and South Korean President Moon Jae-in will meet at the truce village of Panmunjom straddling the Korean border, but a venue for the North Korea-U.S. summit has yet to be decided.
CHINA URGES PATIENCE
U.S. national security adviser H.R. McMaster briefed U.N. Security Council envoys in New York on Monday.
"We all agreed that we're optimistic about this opportunity, but we're determined, we’re determined to keep up the campaign of maximum pressure until we see words matched with deeds and a real progress towards denuclearisation," McMaster said.
South Korean U.N. Ambassador Cho Tae-yul, who attended the McMaster briefing, described the plans for talks with North Korea as a “once in a lifetime opportunity.”
The South Korean officials who met Kim travelled to Washington last week to relay his message and visited China on Monday to brief President Xi Jinping, who urged patience.
South Korea's National Security Office chief, Chung Eui-yong, who led the delegation to Pyongyang, will head to Russia on Tuesday, while spy agency chief Suh Hoon met Japan's foreign minister in Tokyo, where he is to speak with Prime Minister Shinzo Abe on Tuesday.
In Beijing on Monday, Xi told Chung there was an important opportunity for talks.
"At the same time, all sides must exercise patience and be attentive, and show political wisdom, to appropriately face and dispel any problems and interference to resuming the talks process," state media cited Xi as saying.
Xi said China looked forward to smooth talks between the two Koreas and between the United States and North Korea and substantive progress in the denuclearisation process and normalization of ties.
Tensions eased as the Koreas held talks against the backdrop of the Winter Olympics in South Korea last month, but Japan has expressed scepticism and warned that "talks for the sake of talks" would be unacceptable.
Japanese Foreign Minister Taro Kono said after talks with Suh Hoon that Tokyo and Seoul agreed that maximum pressure must be maintained on North Korea until it takes concrete action to address concerns about its weapons programmes.
Kono declined to say what that action should be, but South Korea's presidential Blue House quoted him as saying that the breakthrough on talks with North Korea was a near "miracle".
In Geneva, the U.N. investigator on North Korea told the world body's Human Rights Council that any progress in the nuclear and security dialogue must be accompanied by talks on human rights violations, including political prison camps.
North Korea's state media have lauded the thaw in relations with South Korea. It has continued to warn the United States and Japan against war-mongering, but its rhetoric has been tame compared with threats exchanged at the height of tensions last year.
(Additional reporting by Michael Martina, Ben Blanchard and Lusha Zhang in Beijing, Paul Cersten in Abuja, Michelle Nichols in New York and David Brunnstrom and Eric Beech in Washington; Editing by James Dalgleish and Peter Cooney)