North Korea said Friday that nuclear talks with the United States “will never be resumed” unless Washington halts what Pyongyang said were “hostile acts” and demands of “unilateral disarmament,” warning of a “fiercer” response if this continues.

In a statement carried by the North’s official Korean Central News Agency, an unidentified Foreign Ministry spokesman delivered Pyongyang’s latest warning to the U.S. in the wake of President Donald Trump’s failed summit with leader Kim Jong Un in Hanoi in February.

“We hereby make it clear once again that the United States would not be able to move us even an inch with the device it is now weighing in its mind, and the further its mistrust and hostile acts towards the DPRK grow, the fiercer our reaction will be,” the spokesman said, using the acronym for the North’s formal name, the Democratic People’s Republic of Korea.

“Unless the United States puts aside the current method of calculation and comes forward with a new method of calculation, the DPRK-U.S. dialogue will never be resumed and by extension, the prospect for resolving the nuclear issue will be much gloomy,” the spokesman said.

The Hanoi talks, the second summit between Trump and Kim, collapsed without a deal due to large differences over the scope of North Korea’s denuclearization and potential sanctions relief by the U.S. Reuters reported in March that Trump had passed Kim a note bluntly calling for North Korea to surrender all its nuclear weapons and fuel, a demand he could not abide by.

Nuclear talks between the two countries have languished in the months since, with North Korea delivering criticism of Washington’s position in the negotiations and Kim setting an end-of-the-year deadline for progress.

Friday’s statement said the “underlying cause” of the “setback” in Hanoi was “the arbitrary and dishonest position taken by the United States.”

The U.S. had insisted on “a method which is totally impossible to get through,” it said.

The warning came just a day ahead of Trump’s arrival in Tokyo for a four-day state visit, where he will be the first foreign leader to meet the new emperor and will hold talks with Prime Minister Shinzo Abe. The North’s nuclear arsenal is likely to be high on the agenda for those talks.

It also came after a senior North Korean official warned late last month of an “undesired consequence” if Washington does not adjust its policy by the deadline.

“Our determination for denuclearization remains unchanged, and when the time comes, we will put it into practice. But, this is possible only under the condition that the U.S. changes their current method of calculation and formulates a new stand,” North Korean First Vice Foreign Minister Choe Son Hui, a key figure in negotiations with the United States, said in April.

At a meeting of the North’s rubber-stamp parliament that month, Kim said he is willing to meet with Trump for a third time if Washington comes to the table with the “correct posture” — but laid down his deadline “for a bold decision from the U.S.”

The warning came amid growing tensions between the U.S. and North Korea, which launched a series of short-range missiles over five days earlier this month, bringing a period of more than 500 days without a missile test to an end.

Trump, who has repeatedly touted the halt of North Korean missile tests as one of his top foreign policy achievements, has played down the significance of those tests, calling them “very standard stuff.”

Prior to the recent launches, the North’s last known missile test was in November 2017, when it test-fired a Hwasong-15 intercontinental ballistic missile, which experts believe is capable of striking much, if not all, of the continental United States.

Pyongyang informally adopted a freeze on missile tests from then on, and in April last year declared a “suspension” of nuclear and long-range missile launches.

Vipin Narang, a North Korea expert and professor of international relations at MIT, said Friday’s statement, especially the reference to a “fiercer” reaction, could mean “missile tests might get longer or more frequent.”

“After that …. maybe an ICBM or SLV test,” he wrote on Twitter, referring to the test of an ICBM or a space-launch vehicle, which shares characteristics with long-range missiles.

For now, added Narang, “Trump is in a pickle. Ignore the missile tests and he incentivizes Kim pushing the line. Lash out for something short of an ICBM and risk blowing the whole thing up.”