United States President Donald Trump has said the historic summit with North Korea's Kim Jong-un in Singapore on June 12, 2018 may be delayed.

This is according to the BBC.

Trump was speaking as he received South Korea's President Moon Jae-in at the White House on May 22 (Singapore time) to discuss the summit.

Summit in jeopardy

This appears to be a 180-degree turn from just a day earlier, where the summit was announced to be 99.9 percent on track, South Korean news agency Yonhap reported.

Reassurances were given despite fresh tensions on the Korean Peninsula, Seoul's top security official said on Monday, before Tuesday's surprise delay announcement.

Chung Eui-yong, chief of the presidential National Security Office, made the remarks aboard Air Force One bound for Washington, where Moon met with Trump on Tuesday.

"We believe there is a 99.9 percent chance the North Korea-US summit will be held as scheduled," Chung told reporters. "But we're just preparing for many different possibilities."

Yonhap reported that Moon will "likely tell President Trump what to expect and what not to expect from Kim" on this trip to the US.

North Korean antics

North Korea has recently ratcheted up its criticism.

It hit out against Seoul and Washington, as both of these allies conducted a joint military exercise.

The North has threatened to reconsider holding its first-ever summit with the United States, as it reiterated that the joint military exercise was a rehearsal for invasion and an act of provocation.

It even suspended its high-level dialogue with Seoul originally set for last week.

Pyongyang then accused US national security adviser John Bolton of making "reckless statements".

Bolton had suggested the North could follow a "Libya model" of denuclearisation.

That was a reference to Libya's former leader, Muammar Gaddafi, who agreed to give up nuclear weapons in 2003 and was later killed by Western-backed rebels.

Trump, however, later denied the US would follow the "Libyan model" if an agreement was reached with North Korea.

North Korea has all along threatened to derail talks if the US insisted on it giving up nuclear weapons unilaterally.

Analysis of North Korean rhetoric

Chung said in response to the North's increasingly belligerent rhetoric: "We're trying to understand the situation from the North's perspective."

As for the Moon-Trump summit, Chung said the two leaders will have "candid discussions on how to make the North-U.S. summit a success and produce significant agreements and how to best implement those agreements."

"South Korea and the US have been sharing every bit of information and have remained in close coordination with each other," Chung added.

"We've had various working-level discussions on how to steer North Korea in a direction that we want, and I expect (Moon and Trump) will have great talks this time."

South Korea the middleman

Chung even rejected a recent New York Times article that cited administration and foreign officials.

The piece claimed that Trump had begun pressing his aides about whether going ahead with the summit with Kim Jong-un was worth the risk.

"During phone calls between our two leaders or talks between our National Security Councils, I never got such an impression," Chung said.

Chung also denied the article's claim that Trump asked Moon during their phone conversation on Saturday why the North's statements contradicted Moon's private assurances following the South-North summit in late April.

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