The US special envoy for North Korea has dismissed a year-end deadline set by Pyongyang to make concessions in stalled nuclear talks, but said Washington was ready to resume negotiations at any time.

“Let me be absolutely clear. The US does not have a deadline. We have a goal to fulfil the commitments the two leaders made during their historic summit meeting in Singapore,” Stephen Biegun said on Monday, referring to Donald Trump and Kim Jong-un’s first summit in June last year, when they signed a vague statement on denuclearisation.

Speaking to reporters after meeting the South Korean president, Moon Jae-in, Biegun described recent statements from North Korean officials warning the US to honour the deadline as “so hostile and negative and so unnecessary”.

“We are fully aware of the strong potential for North Korea to conduct a major provocation in the days ahead. To say the least, such an action will be most unhelpful in achieving lasting peace on the Korean peninsula.

“Let me speak directly to our counterparts in North Korea: It is time for us to do our jobs. Let’s get this done. We are here. And you know how to reach us.”

Denuclearisation talks have been stalled since Trump and Kim ended their summit in Hanoi in February without agreement.

Pyongyang has set a year-end deadline for Washington to make concessions, warning that failure to do so would force it to adopt a “new path” that observers believe could include a resumption of long-range missile tests.

Commenting on a series of increasingly belligerent declarations issued by North Korea in recent weeks, Biegun said: “We have heard them all. It is regrettable that the tone of these statements towards the United States, the Republic of Korea, Japan and our friends in Europe have been so hostile and negative and so unnecessary.”

North Korea said at the weekend it had successfully performed another “crucial test” at its long-range rocket launch site. Days earlier, it claimed to have carried out a “very important test” at the same site, prompting speculation that it involved a new engine for either an ICBM or a space launch vehicle.

North Korea’s military chief, Pak Jong-chon, said the North had built up “tremendous power” and that the findings from the recent tests would be used to develop new weapons to enable the country to “definitely and reliably” counter US nuclear threats.

Frustrated by the lack of sanctions relief after three summits with Trump, North Korea has vowed an ominous “Christmas gift” if the US does not come up with concessions by the end of the year.

“What is left to be done now is the US option and it is entirely up to the US what Christmas gift it will select to get,” Ri Thae-song, vice foreign minister in charge of US affairs, said in a statement last week.

North Korea, Ri added, “has done its utmost with maximum perseverance not to backtrack from the important steps it has taken on its own initiative”.

Ri’s challenge to the US fuelled speculation that the North could be preparing to again test intercontinental ballistic missiles capable of reaching the US mainland. An ICBM test at the end of the year would mark a serious blow to Trump, who has cited the regime’s moratorium on nuclear and long-range missile tests as a foreign policy triumph.

Biegun has reportedly not ruled out a meeting with North Korean officials at the truce village of Panmunjom before he is scheduled to leave South Korea on Tuesday.