A new report citing U.S. intelligence agencies says that North Korea has boosted its nuclear fuel production at multiple secret sites in recent months — despite leader Kim Jong Un’s pledge to work toward denuclearization.

The report Friday by NBC News, citing more than a dozen American officials familiar with assessments by analysts at the CIA and other intelligence agencies, comes just weeks after U.S. President Donald Trump’s landmark summit with Kim in Singapore. At the summit, Kim agreed in a vaguely worded joint statement to “work towards the complete denuclearization of the Korean Peninsula.”

Trump has touted this as a major breakthrough with the nuclear-armed North after months of heated rhetoric and weapons tests, claiming in a tweet after the summit that there is “no longer a nuclear threat from North Korea.”

But U.S. officials said the news of continued fuel production means the Kim regime is likely positioning itself to wring every concession it can out of the Trump administration while still clinging to its nuclear weapons, which it sees as crucial to its survival.

Friday’s report said that even as the two sides engaged in diplomatic moves, Pyongyang was stepping up its production of enriched uranium for nuclear weapons. The report quoted five U.S. officials, who cited the latest intelligence assessment.

While the North Koreans have halted missile and nuclear tests, “there’s no evidence that they are decreasing stockpiles, or that they have stopped their production,” said one U.S. official briefed on the latest intelligence. “There is absolutely unequivocal evidence that they are trying to deceive the U.S.”

It said four other officials familiar with the intelligence assessment also said North Korea intended to deceive the U.S.

The officials also said the U.S. had stepped up its intelligence collection against the North, known as the hardest of the hard in terms of espionage targets, and that this gambit was now paying dividends.

In an apparent sign of this, NBC News said it had agreed to withhold some details of the latest intelligence assessment that officials said could put sources at risk.

“There are lots of things that we know that North Korea has tried to hide from us for a long time,” a U.S. intelligence official said.

North Korea has long been known to have at least one undeclared facility to enrich nuclear fuel, aside from Nyongbyon, its main nuclear site.

Experts have long believed that the North likely had multiple secret sites, but the confirmation of it is a new development.

“Work is ongoing to deceive us on the number of facilities, the number of weapons, the number of missiles,” one U.S. intelligence official was quoted as saying. “We are watching closely.”

Vipin Narang, a North Korea expert and professor of international relations at MIT, said Friday that the revelations appeared to be a sign the U.S. intelligence community remains concerned that in declaring victory, the Trump administration was getting far ahead of itself.

“The IC would have briefed Trump on all of this before Singapore — they’ve known this for months,” Narang wrote in a tweet. “The fact that this fire hydrant leak came now suggests they are extremely concerned by Trump declaring ‘mission accomplished’ already.”

U.S. Secretary of State Mike Pompeo is expected to visit North Korea next week, with a trip to Japan to immediately follow his talks in Pyongyang, according to media reports quoting Japanese government sources. The trip, which hasn’t been confirmed by the U.S. State Department, would be his first to the North since the Singapore summit. His visit to Japan for talks with Prime Minister Shinzo Abe and Foreign Minister Taro Kono would be his first official visit to Tokyo as the top American diplomat.

On Saturday, the U.S. State Department said Pompeo had stressed to China the importance of continued enforcement of sanctions on North Korea to press it to give up its nuclear weapons, after warning of signs of backsliding by Beijing.

The State Department said in a statement that Pompeo spoke to Chinese Foreign Minister Wang Yi on Thursday and discussed efforts “to achieve our shared goal of the complete, verifiable, and irreversible denuclearization of the Korean Peninsula.”

Pompeo reiterated that North Korea would have a bright future if it denuclearizes and emphasized “the continued importance of full enforcement of all relevant U.N. Security Council resolutions related to North Korea.”

The statement said this was especially important when it came to preventing North Korea’s illegal export of coal and imports of refined petroleum through ship-to-ship transfers prohibited by the United Nations.

U.S. officials have voiced concern that recent international engagement with Pyongyang could lead countries — China in particular — to ease sanctions pressure on the Kim regime.

Pompeo told a U.S. Senate hearing this week he had seen “modest” backsliding by China, North Korea’s sole patron and main trading partner.

“We have observed China not enforcing control over their cross-border areas as vigorously as they were six or 12 months ago,” Pompeo told the hearing.