SEOUL, South Korea — A second test of what appeared to be an advanced missile engine, part of what North Korea said on Saturday was part of a “reliable strategic nuclear deterrent,” left little doubt that the country is moving quickly toward resuming the program that led to a crisis with Washington two years ago.
While the North gave no details, it said it had conducted “another crucial test” on Friday night at a missile-engine and satellite-launching site that leader Kim Jong-un had once promised President Trump he was about to close. It was the second such test in a week, and came after weeks of increasingly vocal attempts to press the United States into further talks and new concessions.
All the available evidence indicated it was some kind of advanced missile engine, and the wording of the North Korean announcement strongly suggested it was part of a renewal of the country’s nuclear delivery systems.
American analysts and intelligence experts said they believe the ground test — conducted at a stationary stand designed to demonstrate experimental missile-engine designs — was intended as a signal that the country could soon resume testing of an intercontinental ballistic missile.
While the North demonstrated in 2017 that its fleet could likely reach parts of the United States, the country still has not shown it could design a warhead that would survive the heat and huge forces that come with re-entry of a warhead into the atmosphere.
But such a test, both officials and outside analysts speculate, might come within a month, after the expiration of a North Korea-imposed deadline for solid progress with the United States. The American special envoy for Korean nuclear affairs, Stephen Biegun, is in South Korea’s capital, Seoul, this weekend to try to conduct some last-minute diplomacy, perhaps including a meeting with North Korean diplomats at the Demilitarized Zone.
Mr. Biegun has been nominated to become deputy secretary of state and could then become acting secretary should Mike Pompeo resign to run for the Senate from Kansas.
Inside the administration, even President Trump has begun warning that the leader-to-leader diplomacy that he thought would cut through differences is at risk. Until this weekend, North Korean officials have usually avoided describing their renewed efforts as part of a military nuclear program.
But they have now dropped that pretense.
Any significant missile or nuclear test would unambiguously contradict Mr. Trump’s assertion that he has already changed the North’s behavior. And it would pose the risk of a renewed confrontation in the midst of the president’s re-election campaign. Mr. Trump tweeted last week that the North should not “interfere” in the election.
A ground test alone does not change the North’s ability to strike at its neighbors. But it suggests a full-scale resumption of activity Mr. Trump had been told was suspended.
Michael Elleman, the director of nonproliferation and nuclear studies at the International Institute for Strategic Studies, tweeted on Saturday that “these ground tests benefit the DPRK strategic capabilities considerably, so they serve technical and political imperatives.”
The test was successfully conducted on Friday night at the “Sohae Satellite Launching Ground,” a spokesman of the North’s Academy of Defense Science said. That was a reference to facilities in Tongchang-ri, near the North’s northwestern border with China, where it also said it had conducted a “a very important test” last Saturday.
South Korean officials have said that the earlier test was of an engine that could power either a satellite-carrying rocket or a ballistic missile.
On Saturday, the North Korean spokesman said the successful results of both tests would “be applied to further bolstering up the reliable strategic nuclear deterrent” of North Korea, according to the North’s official Korean Central News Agency.
In a separate statement on Saturday, Pak Jong-chon, the chief of the general staff of the North Korean People’s Army, said the data from the latest tests would help develop “another strategic weapon” to deter the United States.
“We should be ready to cope with political and military provocations of the hostile forces, and be familiar with both dialogue and confrontation,” Mr. Pak said. He said the United States and other forces would “spend the year-end in peace only when they hold off any words and deeds rattling us.”
Mr. Pak’s comments suggested that the tests could have been for an engine for an intercontinental ballistic missile, said Cheong Seong-chang, the vice president of research planning at the Sejong Institute in South Korea. The statement also signaled that, as diplomacy stalled, the voice of North Korea’s hard-line military was rising, Mr. Cheong said.
North Korea has repeatedly indicated that it would abandon diplomacy and could resume weapons tests unless Washington met a Dec. 31 deadline — set by Mr. Kim — for the United States to return to the negotiating table with more concessions, including the easing of international sanctions.
Mr. Kim is widely expected to use a meeting of his Workers’ Party’s Central Committee, scheduled for this month, and his annual New Year’s Day speech to reveal his new policy options.
The resumption of activities at Tongchang-ri, where a satellite was last launched in February 2016, has worried officials in Washington, Seoul and Tokyo because the site houses facilities to test rocket engines and launch satellite-delivery vehicles.
Although North Korea insists that its space program is peaceful, Washington and its allies said that the program was a front for efforts to build and test technologies for intercontinental ballistic missiles. A series of resolutions by the United Nations Security Council ban North Korea from testing ballistic missile technology.
In March 2017, North Korea successfully tested a high-thrust engine at Tongchang-ri that it used in intercontinental ballistic missiles, such as the Hwasong-14 and Hwasong-15, later that year. Analysts fear that North Korea might now be preparing to launch another long-range rocket carrying a satellite or even to flight-test a long-range missile.
The country conducted its last ICBM test from Pyongsong, north of Pyongyang, the North Korean capital, in November 2017. Afterward, Mr. Kim declared a halt on all nuclear and ICBM tests and embarked on diplomacy with President Trump.
Mr. Kim met with Mr. Trump in Singapore in June 2018 and agreed to “work toward complete denuclearization of the Korean Peninsula” in return for “new” relations and security guarantees from Washington. After the Singapore meeting, Mr. Trump boasted that Mr. Kim had promised to dismantle the Tongchang-ri facilities as one of the first steps toward denuclearization.
North Korea started to dismantled the missile-engine test facility that summer, but then rebuilt it, after Mr. Kim’s subsequent meetings with Mr. Trump and negotiations between diplomats failed to resolve differences over how to implement the broadly worded Singapore deal.
North Korea has also resumed the test of mostly short-range ballistic missiles and rockets this year. Mr. Tump has largely dismissed such tests as involving weapons that do not directly threaten the United States.
If North Korea returned to launching satellites or testing ICBMs, it could seriously dent Mr. Trump’s foreign-policy credentials. Mr. Trump has repeatedly cited Mr. Kim’s self-imposed moratorium on nuclear and ICBM tests as one of his major achievements.
Photo: © Pedro Ugarte/Agrence France-Presse – Getty Images North Korean soldiers at Tongchang-ri in 2012. The site once tested engines that were used in long-range missiles.