"The discussions are just getting started, so we are still waiting to see how they come out, but depending on their outcome, the president could join President Trump and Chairman Kim in Singapore", the official said.
Trump tweeted a day after he and Kim separately expressed willingness to meet June 12 in Singapore as originally planned, after the US leader abruptly canceled the summit on Thursday, citing the North's "open hostility".
In addition to the border talks, White House spokeswoman Sarah Huckabee Sanders said a "pre-advance team" left for Singapore on Sunday morning to work on logistics for a possible summit.
"I support the letter that President Trump sent to Kim Jong Un", Clapper said.
The meeting was the latest dramatic turn in a week of diplomatic ups and downs surrounding the prospects for an unprecedented summit between the USA and North Korea, and the strongest sign yet that the leaders of the two Koreas are trying to keep the on-again off-again meeting on track.
Sung Kim, a former United States ambassador to South Korea and former nuclear negotiator with the North, has been called in from his posting as envoy to the Philippines to lead the preparations, according to a person familiar with the arrangements.
The Washington Post first reported that the team, which also included Allison Hooker, the Korea expert on the White House National Security Council, met with Choe Son-hui, the North Korean vice foreign minister.
Howard X said Kim's rise as the third leader of North Korea in 2011 has proved lucrative for him, jump starting a new career in films, commercials and private functions, most often in his home town of Hong Kong.
Mr. Moon told reporters Sunday that Mr. Kim at a meeting at the Demilitarized Zone that separates the two Koreas "again made clear his commitment to a complete denuclearization of the Korean Peninsula".
NFL Will Fine Teams if Players Don't Stand for National Anthem
Johnson previously spoke out against the possibility of adopting any kind of policy requiring players to stand for the anthem. Trump criticized players kneeling during the anthem during a rally last fall.
Washington wants North Korea to quickly give up all its nuclear weapons in a verifiable way in return for sanctions and economic relief.
Pyongyang has rejected unilateral disarmament and has always couched its language in terms of denuclearisation of the Korean Peninsula.
American officials are sceptical that Kim will ever fully abandon his nuclear arsenal.
"What Kim is unclear about is that he has concerns about whether his country can surely trust the United States over its promise to end hostile relations (with North Korea) and provide a security guarantee if they do denuclearization", Mr. Moon said.
"They're playing a game", Rubio said of North Korea, which three months ago announced the successful testing of a complete deterrence system that includes thermonuclear warheads as well as intercontinental ballistic missiles capable of striking the USA mainland.
-North Korea summit in June, government officials said Sunday.
Kim, in a dispatch issued by the North's state-run news service earlier Sunday, "expressed his fixed will on the historic (North Korea)-U.S. summit talks".
James R. Clapper Jr., a former director of national intelligence and a onetime senior intelligence officer for US forces in South Korea, said he anxious that Trump may be opening the United States to demands that it scale back its strategic forces in the Pacific.
Seeking a denuclearisation deal with North Korea was a top priority for a leader who came to the White House on a political promise of putting "America first" while withdrawing from worldwide agreements on climate change and Iran.