Washington, Mar 1 (IANS): US President Donald Trump held phone conversations with leaders of South Korea and Japan over the Hanoi summit during his flight en route to Washington, the White House has said.

White House Press Secretary Sarah Sanders told the press on Thursday that Trump had updated South Korean President Moon Jae-in and Japanese Prime Minister Shinzo Abe on his meeting with North Korean leader Kim Jong-un, Xinhua reported.

Trump told the two leaders that his administration would "continue the conversations" with Kim and continue to coordinate closely with the allies, Sanders said.

US Secretary of State Mike Pompeo, who was on his trip to Manila, told reporters that Washington had not set a date for next working-level meeting with Pyongyang, adding that the two sides "need to regroup a little bit".

Trump and Kim ended their second summit in Hanoi on Thursday without reaching an agreement.

Trump said at a press conference that there was "a gap" in what North Korea and the US were pursuing.

Kim demanded relief from sanctions against Pyongyang "in their entirety" in exchange for denuclearizing a "large portion" of North Korea's nuclear programme, something the US could not agree to, according to Trump.

However, North Korean Foreign Minister Ri Yong Ho said at a separate news conference in Hanoi on early Friday that "what we proposed was not the removal of all sanctions, but they are partial removal," adding that North Korea only asked those sanctions impeding the livelihood of its people to be removed first.

"It is regrettable that President Trump and Chairman Kim were unable to reach complete agreement," Kim Eui-keum, spokesman for South Korean President Moon Jae-in, told a press briefing.

The Blue House spokesman, however, noted that it seemed clear that the two leaders have made "more meaningful progress" than ever as they expanded the scope and depth of their understanding of each other's positions through the two-day summit in the Vietnamese capital.