North Korea on Wednesday abruptly threatened to cancel the hotly anticipated summit between leader Kim Jong Un and U.S. President Donald Trump if Washington presses ahead with its demand that Pyongyang unilaterally relinquish its nuclear arsenal.

Citing a top nuclear negotiator, the North’s official Korean Central News Agency (KCNA) served up a harsh criticism of the White House’s recent language on ridding the country of its weapons of mass destruction — the first major sign of trouble amid warming ties.

If the Trump administration “is trying to drive us into a corner to force our unilateral nuclear abandonment, we will no longer be interested in such dialogue and cannot but reconsider our proceeding to the DPRK-U.S. summit,” First Vice Foreign Minister Kim Kye Gwan said in the statement. DPRK is the acronym for the North’s formal name, the Democratic People’s Republic of Korea.

Kim Kye Gwan, a top diplomat involved in past nuclear talks with the U.S., said the future prospects for the Kim-Trump summit, as well as improvements in overall bilateral ties, would “be crystal clear” if Washington continued to speak of a “Libya-style” denuclearization for the North.

The statement singled out national security adviser John Bolton, known for his hawkish stance on North Korea, for pushing the Libya model, as well as the “complete, verifiable and irreversible denuclearization” (CVID) of the North and the “total decommissioning” of its nuclear weapons, ballistic missiles and biological and chemical weapons.

“We shed light on the quality of Bolton already in the past, and we do not hide our feeling of repugnance towards him,” it said.

After Bolton was critical of North Korea’s human rights record in 2003, state-run media described him as “human scum” and a “bloodsucker.”

“This is not an expression of intention to address the issue through dialogue,” the statement said. “It is essentially a manifestation of awfully sinister move to impose on our dignified state the destiny of Libya or Iraq which had been collapsed due to yielding the whole of their countries to big powers.”

North Korea has routinely pointed to U.S. military interventions as justification for its nuclear weapons program, citing in 2013 “the tragic consequences in those countries which abandoned halfway their nuclear programs” — an allusion, in particular, to Libya and its late leader, Moammar Gadhafi, who was sodomized with a bayonet before being shot dead immediately after his capture in 2011.

Gadhafi had agreed in 2003 to roll back his own decades-old nuclear program in exchange for the lifting of economic sanctions and a return to the international community.

Still, Kim Kye Gwan warned against comparisons to the two toppled dictatorships, saying “it is absolutely absurd to dare compare the DPRK, a nuclear weapon state, to Libya which had been at the initial stage of nuclear development.”

The statement also ruled out accepting any deal with the U.S. that saw the North trade away its “treasured nuclear sword” in exchange for economic rewards and benefits.

James Schoff, an East Asia expert with the Carnegie Endowment for International Peace in Washington, said the targeting of Bolton was telling, “since he has been the most demanding” Trump official in regards to the Libya model, early CVID — and even in pushing for addressing issues that have been major concerns for Japan, including other weapons of mass destruction such as chemical and biological weapons and short- and midrange ballistic missiles that can target the country.

Bolton has also been outspoken on the need to resolve the issue of Japanese nationals abducted by North Korean agents in the 1970s and 1980s.

“In a way, the North is forcing Trump to show his inclination to support Bolton or perhaps a less demanding form of ‘denuclearization’ that simply reduces the threat to the U.S.,” Schoff said. “Trump could go either way — because he seems to want a deal — so we’ll learn something from his reaction.”

Schoff said that “if he … distances his view from Bolton, then (Prime Minister Shinzo) Abe and Japan will be disappointed, because it will seem more likely that Trump is willing to let Japan’s needs fade to the background in favor of his own political gain.”

On Wednesday, Japanese Foreign Ministry spokesman Toshihide Ando pledged that Tokyo will keep a close eye on actions and announcements by Pyongyang, while adding that the government would continue to work closely with the U.S. toward a successful Kim-Trump summit.

“Through the U.S.-North Korea summit, we hope to see progress in denuclearization, the abandonment of missiles, and most importantly, the abductee issue,” Ando said.

North Korea’s ruling party newspaper, the Rodong Sinmun, lashed out Wednesday at attempts by Tokyo to urge Washington to address the nuclear and missile programs at the summit, calling the moves “desperate efforts” by a “trouble-maker creating only complexities.”

“There is a way for it to evade the fate of being left out alone in the region,” it said. “It is to give up its hostile policy towards the DPRK.”

In a separate dispatch earlier Wednesday, KCNA had called into question the Kim-Trump summit and blasted moves by the South after canceling high-level talks scheduled for later in the day with Seoul, citing joint U.S.-South Korean air force drills known Max Thunder.

“If the U.S. and the south Korean authorities regard the phase of improving inter-Korean ties and the DPRK-U.S. dialogue … as something allowed any time and any hour, then they are sadly mistaken,” KCNA said.

“There is a limit in showing goodwill and offering opportunity.”

Washington, KCNA said, will “have to undertake careful deliberations about the fate of the planned North Korea-U.S. summit in light of this provocative military ruckus.”

The United States said it will continue to plan for the Kim-Trump meeting, scheduled for June 12 in Singapore, with State Department spokeswoman Heather Nauert saying that it had received “no notification” of a change in position by North Korea.

The State Department has “not heard anything from (the North Korean) government … to indicate we would not continue conducting these exercises or would not continue planning” for the Kim-Trump summit, Nauert said.

The White House said it was examining the statements.

The North Korean moves appeared to be a dramatic return to the blistering rhetoric that Pyongyang had traded with Washington and Seoul ahead of the thaw in relations earlier this year between the North and the two allies.

South Korean Unification Ministry spokesman Baek Tae-hyun said the North’s decision “does not conform with the spirit and purpose” of last month’s inter-Korean summit, where the Koreas’ leaders issued a vague pledge on the “denuclearization of the Korean Peninsula” and vowed to work toward a permanent peace.

That growing detente saw South Korean President Moon Jae-in meet with Kim at the truce village of Panmunjom in the Demilitarized Zone (DMZ) for the rare inter-Korean leaders’ talks, helping lay the groundwork for the Kim-Trump summit.

High-level talks between the two Koreas were planned to take place at the DMZ on Wednesday to discuss follow-up measures to the Panmunjom summit, but the North — in a notice sent to the South around 12:30 a.m. that day — postponed the meeting “indefinitely,” according to the Unification Ministry.

The first KCNA dispatch blamed the cancellation on the Max Thunder drills, which it called an “undisguised challenge to the Panmunjom Declaration” and said were taking place before the “ink of the … historic declaration” had dried.

It called the two-weeklong exercise, which kicked off last Friday, “a bid to make a preemptive airstrike … and win the air.” The KCNA report specifically cited the deployment of nuclear-capable B-52 bombers, likely those based on the U.S. territory of Guam, as well as advanced F-22 stealth fighter jets as evidence of menacing behavior by the U.S.

North Korea has lambasted past exercises involving the B-52 and the B-1B bomber, which is not nuclear capable. It has blasted the flights by “the air pirates of Guam” as rehearsals for striking its leadership, calling them “nuclear bomb-dropping drills.”

South Korea’s Yonhap news agency said Wednesday that the U.S. would not send B-52s for the drills. The exercises will include about 100 aircraft, including F-22s, the report said, citing unidentified South Korean military and government officials.

The Pentagon did not answer emailed questions about that report, but called the drills “routine” and “defensive exercises.”

The North has routinely condemned the joint military drills as practice for invasion, and major exercises, usually around March, have often sent tensions on the peninsula soaring.

But in this year’s diplomatic rapprochement the allies had postponed those drills, known as Key Resolve and Foal Eagle, until after the Olympics and Paralympics in Pyeongchang, as Moon sought to secure the North’s participation at the games.

In response, envoys from Seoul who met with Kim said the North Korean leader had told them he would “understand” if the exercises went ahead.

The postponed drills were later held with little of the rhetorical flourishes typically associated with North Korea’s state media apparatus — a trend that continued until Wednesday.

The North, subject to crushing sanctions — part of Trump’s “maximum pressure” campaign — could be using the threat of a canceled Kim-Trump summit and an end to improving ties with South Korea as leverage to ease those measures.

Van Jackson, a North Korea expert at Victoria University of Wellington in New Zealand, said that Pyongyang could be “putting out a test to see if all the nice-nice rhetoric and summitry will translate into concessions from either the U.S. or South Korea.”

“If the alliance exercises proceed, that’s an indication that the alliance isn’t going to bend for North Korea and maximum pressure may remain in place for a while,” Jackson said. “If the alliance curtails its exercises in the name of diplomatic engagement, North Korea knows it’s got a soft target — it will have greater room to press for greater demands.”

Pyongyang has a long history of toggling from aggression to engagement, or vice versa, in a bid to win concessions.

“This latest move on North Korea’s part is only surprising if you take North Korean leader Kim Jong Un at his word that he doesn’t have a problem with joint U.S.-South Korean military exercises,” said Jean Lee, a North Korean expert at the Wilson Center think tank in Washington. “This serves as a reminder that the North Koreans are tricky operators, and that everything we’ve heard leader Kim Jong Un promise must be considered with skepticism.”

Lee said the news would likely be disappointing to the South Koreans although not altogether surprising — though it would come as a jolt to Trump, who has helped push expectations for a successful summit sky-high.

“The North Koreans routinely play emotional blackmail with the South Koreans by walking away from highly anticipated talks at the last minute,” she said. “It will serve as a wake-up call to President Trump, who may have been too bold in prematurely claiming victory when the push and pull of negotiations with the savvy North Koreans has only just begun.”