North Korea has expanded a factory linked to the production of long-range nuclear missiles, according to a new analysis of satellite photos provided to NBC News that bolsters a growing expectation the country soon will resume testing a capability that threatens the United States.

Commercial satellite images from Planet Labs show a temporary structure at the site to accommodate the raising of a launcher arm, according to Jeffrey Lewis, director of the East Asia Nonproliferation Program at the Middlebury Institute of International Studies.

“We believe North Korea erects this structure when the facility is involved in producing or modifying ICBM launchers,” Lewis concluded in a written analysis, using the acronym for intercontinental ballistic missiles.

North Korea has expanded the March 16 Factory in Pyongsong, a facility associated with the production and modification of ICBM launchers. The March 16 Factory produces both military and civilian vehicles. Russian truck maker KamAZ began participated in a joint venture from November 2006-2010 at the facility to produce to produce civilian vehicles. Planet Labs

This is one of many pieces of evidence pointing in one direction, Lewis added in an interview.

“There is activity at a number of locations indicating that North Korea is laying the groundwork for an expansion of their ICBM program — more systems, more buildings, more capabilities,” he said.

The new evidence comes as U.S. military and intelligence officials are increasingly concerned that North Korea is poised to conduct a long-range missile test in the next few days or weeks, an act that would signal the final breakdown of diplomatic talks that President Donald Trump has hailed as a signature foreign policy achievement.

Kim Jong Un’s regime has recently warned of an imminent “Christmas gift,” to the United States, and the U.S. Air Force’s top general in the Asia-Pacific region said last week he believes that "gift" could be the test of a long-range ballistic missile.

Commercial imagery taken by Planet Labs shows that North Korea began expanding the site shortly after Kim's visit in June, including constructing a new building that is connected to the one where Kim Jong Un witnessed preparations for the Hwasong-15 launch in 2017. Planet Labs

The country halted nuclear and long-range missiles tests in 2017 in the wake of diplomatic talks with the United States that included two summit meetings between Kim and Trump. But in recent months no progress has been apparent.

“What I would expect is some kind of long-range ballistic missile would be the ‘gift,’” Gen. Charles Brown, head of Pacific Air Forces, told reporters Dec. 17. “Does it come on Christmas Eve? Does it come on Christmas Day? Does it come after the new year? One of my responsibilities is to pay attention to that.”

The Air Force will be prepared to respond to a missile launch, Brown said, without being specific. “There’s a lot of stuff we did in 2017 that we can dust off fairly quickly and be ready to use," he said.

The facility flagged by Lewis and his team is known as the March 16 Factory, and it produces both military and civilian vehicles. Russian truck maker KamAZ began participating in a joint venture at the facility to produce civilian vehicles from November 2006 to 2010, Lewis said.

Kim visited the facility in August 2017. Although North Korea presented the trucks he viewed as civilian vehicles, the same type of trucks were seen in military parades in 2017 and 2018 transporting ICBMs, Lewis said.

Kim visited the factory again in December 2017 to watch preparations for the launch of a Hwasong-15 ICBM. North Korean tests of mobile missiles tend to be conducted from factories involved in the production of the launcher.

Kim appears to have visited part of the facility a third time in June 2019, Lewis says, and commercial imagery taken by Planet Labs shows that North Korea began expanding the site shortly after that visit. Among the additions was a new building that is connected to the one where Kim witnessed preparations for the Hwasong-15 launch in 2017.

“An expansion of the plant increases its capability to produce trucks for both civilian and military use,” Lewis wrote. “Until now, North Korea’s limited ability to produce heavy-duty vehicle chassis has been a constraint on the development of a survivable intercontinental-range ballistic missile program. The expansion of this facility may represent an increase in North Korea’s ability to produce domestic missile launchers and expand its ICBM force.”

When North Korea conducted a series of long-range missile tests in 2017, Trump threatened the nation with “fire and fury.” If it resumes the tests, Trump will find himself, as every recent president has, with no palatable choices. A military strike against the North risks a war that could cost hundreds of thousands of South Korean lives.

“The only option is to accept the reality that North Korea is a nuclear-armed state that holds the U.S. at risk,” Lewis said. “The Trump administration had an opportunity, and I think they’ve blown it.”

Kim was never willing to disarm, Lewis said, but he may have been prepared to “have those weapons recede from view, stop testing, stop showing them off at parades, stop threatening people with them.”

But Trump insisted that North Korea would have to give up its weapons entirely, something the U.S. intelligence community has assessed as extremely unlikely.

Trump appeared to make a direct appeal to Kim earlier this month, when he tweeted: “Kim Jong Un is too smart and has far too much to lose, everything actually, if he acts in a hostile way. 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.”

Trump’s special envoy, Stephen Biegun, on a visit to South Korea this month urged the North back to the negotiating table.

"Let me speak directly to our counterparts in North Korea," he said. "It is time for us to do our jobs. Let's get this done. We are here, and you know how to reach us."