SEOUL — North Korea said Sunday that it had conducted a “very important test” at a rocket launch site, even as a senior diplomat said denuclearization is off the negotiating table.

The test paves the way for North Korea to launch a satellite or intercontinental ballistic missile (ICBM) around the end of this year, experts said, fulfilling a threat to give the United States an unwelcome “Christmas gift.”

A spokesman for North Korea’s Academy of National Defense Science said the test was carried out Saturday at the Sohae Satellite Launching Station in Tongchang-ri, a site near the Chinese border that has been used to launch satellites into space in the past. The United Nations bans North Korea from launching satellites, viewing it as a cover for testing ballistic missile technology.

President Trump earlier said he had persuaded North Korean leader Kim Jong Un to close the site when the pair met in Singapore in June 2018. When evidence emerged that North Korea was rebuilding the site, Trump said in March that he would be “very, very disappointed” with Kim if that proved to be the case but that he didn’t believe it would be.

On Sunday, he again expressed confidence that Kim would not betray their agreement, but he also made an implicit threat to the North Korean leader.

“Kim Jong Un is too smart and has far too much to lose, everything actually, if he acts in a hostile way. He signed a strong Denuclearization Agreement with me in Singapore,” Trump wrote on Twitter.

“He does not want to void his special relationship with the President of the United States or interfere with the U.S. Presidential Election in November. North Korea, under the leadership of Kim Jong Un, has tremendous economic potential, but it must denuclearize as promised. NATO, China, Russia, Japan, and the entire world is unified on this issue!”

Harry Kazianis, senior director of Korean studies at the Center for the National Interest, tweeted that North Korea won’t like Trump’s comment about Kim having “everything to lose.”

“That won’t go over well, not one bit,” Kazianis tweeted.

Saturday’s test underlines just how far bilateral relations have deteriorated since a failed summit in Hanoi at the end of February and could presage a new round of weapons tests and hostile exchanges next year.

In a statement carried by the state-run Korean Central News Agency on Sunday, a North Korean spokesman said the test result “will have an important impact on changing the strategic position of the DPRK,” referring to his country by the initials of its official name, the Democratic People’s Republic of Korea.

Kim Song, Pyongyang’s envoy to the United Nations, dismissed the Trump administration’s calls for dialogue Saturday as a “timesaving trick” aimed solely at “its domestic political agenda.”

“We do not need to have lengthy talks with the U.S. now, and denuclearization is already gone out of the negotiating table,” he said.

Since assuming the presidency, Trump has met with the North Korean leader three times to persuade him to give up nuclear weapons. Trump has repeatedly touted his “good relationship” with Kim as a win from his engagement efforts.

However, North Korea has been ramping up provocations ahead of the year-end deadline it has set for Washington to make a significant concession in nuclear negotiations. Pyongyang has called on the United States to drop its push for unilateral denuclearization of North Korea and relieve punishing sanctions on the country.

The announcement of a new test at the Sohae site is “a first solid step in ending a moratorium on testing” in a lead-up to the end-of-year deadline, said Nathan Hunt, an independent defense analyst who focuses on North Korea’s weapons systems.

Kim announced an end to nuclear warhead and long-range missile tests even before meeting Trump, something the U.S. president has held up as an important diplomatic achievement.

“North Korea is not going to any longer let actions be dictated so as to give good PR to the West,” Hunt said.

Jeffrey Lewis, director of the East Asia Nonproliferation Program at the Middlebury Institute of International Studies, had predicted last week that a test was imminent at Sohae, based on analysis of satellite imagery.

“The North Korean statement strongly implies that North Korea has tested a new or substantially improved rocket engine,” he said Sunday. “This suggests the ‘Christmas gift’ that North Korea has promised will be a new missile. Possibilities range from an improved Hwasong-15 to a solid-propellant ICBM.”

Andrei Lankov, a professor at Kookmin University in Seoul, said Sunday that a satellite test would be the perfect next step because it would not technically breach the moratorium, even if it would be widely seen as an ICBM test in disguise.

“The North Koreans will have no choice, but do something dramatic early next year — after all, they promised that they will not remain idle if the Americans do not give them what they expect,” he wrote in an email.

A satellite test “will not probably produce enough political and media noise they now badly need, so it will be followed by more ‘military demonstrations,’ ” he added.