WASHINGTON, Feb. 28 (Xinhua) -- U.S. President Donald Trump on Thursday held phone conversations with leaders of South Korea and Japan over the Hanoi summit during his flight en route to Washington, according to the White House.

White House Press Secretary Sarah Sanders told the press that Trump had updated South Korean President Moon Jae-in and Japanese Prime Minister Shinzo Abe on his meeting with Kim Jong Un, top leader of the Democratic People's Republic of Korea (DPRK).

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

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 the DPRK and the United States were pursuing. Kim demanded relief from sanctions against Pyongyang "in their entirety" in exchange for denuclearizing a "large portion" of the DPRK's nuclear program, something the United States could not agree to, according to Trump.

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

"It is regrettable that President Donald Trump and Chairman Kim Jong Un 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.