HANOI, Vietnam — In the eight months since President Trump declared North Korea “no longer a nuclear threat,” the reclusive state has advanced both its nuclear weapons and ballistic missile programs and failed to provide an accounting of its deadly arsenal, according to multiple U.S. intelligence assessments.

And intelligence officials tell NBC News they have grown increasingly doubtful that Kim intends to dismantle the nuclear program at the center of Trump’s diplomatic gamble with Pyongyang.

Trump has said an end to North Korea’s nuclear weapons program is his goal. So far, there is no public evidence that it is shared by North Korean leader Kim Jong Un. With just two days before the leaders are set to meet, the White House is setting low expectations for the second summit this week in Vietnam while senior U.S. officials and North Korea experts are expressing mounting concerns that Trump will give away more than he gets in return.

“One of the worst possible outcomes is he makes some crazy deal pledging to withdraw U.S. troops for a vague promise of denuclearization,” said one former senior U.S. official.

Among the possible incentives the U.S. could offer North Korea during the summit is to establish diplomatic interests sections, one in Pyongyang and one in Washington, according to current and former U.S. officials. The establishment of interests sections, which are bare-bones diplomatic outposts, would offer an unprecedented initial opening toward diplomatic relations between the two nations.

The U.S. could also offer to formally end the war on the Korean Peninsula, more than six decades after North Korea and the United Nations Command signed the 1953 Armistice Agreement. This option would involve a series of further meetings and negotiations to determine the fate of the Korean Demilitarized Zone and the future of U.S. troops on the Peninsula.

Asked whether withdrawing U.S. troops from the Korean Peninsula could be a topic of discussion during the Hanoi meeting, Trump said last week "that is not one of the things on the table." Pressed on the issue, he later said, "Everything is on the table."

Some senior Trump administration officials and others involved in the negotiations are worried that establishing interests sections and agreeing to an end of war declaration, in addition to a second presidential meeting for Kim, would amount to de facto U.S. recognition of North Korea as a nuclear state. That’s particularly concerning, officials said, if Trump does not get significant concessions from North Korea.

It’s unclear whether Trump will offer Kim any immediate economic sanctions relief, or hold that as a future concession if North Korea makes some concessions of its own.

Some U.S. officials and others in the region have pushed for Trump to approve waivers on U.S. sanctions against North Korea as an incentive that stops short of rolling back sanctions entirely. The U.S. could also ask the U.N. to do the same for international sanctions, officials said.

The two leaders could also discuss a possible escrow account for North Korea to use for infrastructure projects in the country that would be funded by the World Bank, South Korea, Japan and others.

In recent weeks alone, researchers have discovered a secret ballistic missile base in North Korea — one of as many as 20 undisclosed missile sites in the country. U.S. officials also acknowledge that North Korea has increased its production of fuel for nuclear weapons at multiple secret sites, all since Trump and Kim first met last summer.

Just last month, National Intelligence Director Dan Coats told congress that "North Korea will seek to retain its WMD capabilities, and is unlikely to completely give up its nuclear weapons and production capabilities." Coats said the "assessment is bolstered by our observations of some activity that is inconsistent with full denuclearization.” Kim and his advisers, Coats said, "view nuclear weapons as critical to regime survival."

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

Trump — a vocal skeptic of his own intelligence agencies — has reportedly cast doubt on classified assessments regarding North Korea’s capabilities. He reportedly told U.S. intelligence officials that he does not believe their assessment that North Korea has sophisticated missile capabilities because Russian President Vladimir Putin told him Pyongyang doesn’t have them, according to a new book by former deputy FBI Director Andy McCabe, a sharp Trump critic.

On Sunday, Trump tweeted lavish praise for Kim, who succeeded his father as head of a brutal, repressive regime that is among the world’s foremost violators of human rights.

Chairman Kim realizes, perhaps better than anyone else, that without nuclear weapons, his country could fast become one of the great economic powers anywhere in the World. Because of its location and people (and him), it has more potential for rapid growth than any other nation! — Donald J. Trump (@realDonaldTrump) February 24, 2019

But the president also projected uncertainty on the eve of his departure. Noting that he and Kim both "expect a continuation of progress made at our first summit in Singapore," Trump ended one tweet with a question: "Denuclerization?" he seemed to publicly ask his North Korean counterpart.

Very productive talks yesterday with China on Trade. Will continue today! I will be leaving for Hanoi, Vietnam, early tomorrow for a Summit with Kim Jong Un of North Korea, where we both expect a continuation of the progress made at first Summit in Singapore. Denuclearization? — Donald J. Trump (@realDonaldTrump) February 24, 2019

Just days after the two men met in a historic first summit last June, Trump proclaimed that North Korea was no longer a nuclear threat. Missile testing has halted, a red line that Trump has used to measure success.

But even his own secretary of state, Mike Pompeo, charged after the Singapore summit with leading negotiations, seemed to differ with the president’s early assessment.

Asked Sunday on CNN whether North Korea remains a nuclear threat, Pompeo answered simply: Yes. And he said that in the first meeting last year, Kim had promised to dismantle his nuclear weapons program.

Pompeo refused to articulate any specific goals for this week's summit. "I don’t want to get into the details of what’s being proposed, what the offers and counter offers may be. But a real demonstrable, verifiable step is something that I know President Trump is very focused on achieving."

Pompeo insisted that the toughest sanctions would remain in place until the nuclear weapons program was dismantled. But he held out carrots. "There are other things we can do," he said, "exchanges of people, lots of other ways that North Korea is sanctioned today that if we get a substantial step and move forward we could certainly provide an outlet which would demonstrate our commitment to the process as well."

U.S. officials believe Kim’s primary goal in Vietnam, where he will be feted with the trappings of a state visit, is to be photographed once more alongside Trump on the world stage.

"Kim already got one big photo op with President Trump, another one just reaffirms his standing on the world stage to every day North Koreans," said one U.S. official.

U.S. officials expect Trump and Kim to discuss the fate of the upcoming joint U.S.-South Korea military exercises, held every spring. After the summit in Singapore, Trump announced he agreed to suspend the joint military exercises, declaring them "very provocative."

Despite intelligence reports that North Korea has continued to refine and expand its nuclear and missile development program while negotiating with the U.S., Trump has stressed that Pyongyang has not launched any missile tests during that time. But a lack of testing does not mean North Korea’s capabilities haven’t advanced on Trump’s watch.

"The North Koreans have the same nuclear arsenal that they had last year," former CIA Director John Brennan said Friday on MSNBC.

"They had probably increased their capabilities," Brennan said. "They don’t have to test in order to maintain and also to further refine that program."

The question looming over the Hanoi summit is whether North Korea will agree to disclose elements of its program it has concealed and agree to freeze work on them in the future.

Another concern voiced by some U.S. officials and North Korea experts is that Trump may announce that Kim agreed to dismantle defunct missile test sites and destroy other elements of his nuclear program that Pyongyang already no longer uses or has opened to inspections in the past.

One measure of success coming out of Hanoi could be agreement from both sides to hold a regular schedule of meetings.

Ultimately, U.S. officials said they hope North Korea agrees to four-party talks that would include the U.S., South Korea and China. If those talks advance, officials said, the Trump administration could then bring in Japan and Russia.

After the fiery rhetoric between the U.S. and North Korea in 2017 that included Trump referring to Kim as "little rocket man," the president now talks about the close relationship between the two. "He wrote me beautiful letters. And they're great letters. We fell in love," Trump said at a rally in September.

This past weekend, Trump tweeted "Great relationship with Chairman Kim!"

While the Singapore Summit did not lead to North Korea halting its nuclear program, it opened negotiations between the two nations at the highest level and further decreased tensions at home and along the Korean peninsula where 28,500 U.S. troops are stationed.

But after the June meeting, progress stalled and some follow on meetings, like one with Pompeo in November, were abruptly canceled. In August, President Trump appointed Stephen Biegun Special Envoy to North Korea, but he was not able to meet with the North Koreans until January.

Pompeo has layered himself with Biegun, according to U.S. officials, with the hope the special envoy will absorb any shortcomings or negative outcome of negotiations with North Korean officials in coming weeks and months.

In a surprise move late Friday night, the White House announced national security adviser John Bolton canceled his trip to South Korea ahead of the summit. "Ambassador Bolton has canceled his travel to the Republic of Korea to focus on events in Venezuela," an administration official said.

Carol E. Lee reported from Hanoi, and Courtney Kube from Washington.