Evidence of new efforts by Kim Jong Un to expand his nuclear arsenal underscore the challenge facing President Donald Trump three weeks after declaring that North Korea was “no longer a nuclear threat.”

Several reports released in recent days suggest that Kim continued to ramp up his weapons production — rather than prepare to disarm — in the weeks leading up to his June 12 summit with Trump in Singapore. The reports published by independent researchers and media organizations detail expansion efforts to increase fuel production, build more missile launchers and expand a key rocket-engine manufacturing facility.

The moves illustrate how far Kim remains from surrendering his nuclear weapons despite committing to “work toward complete denuclearization of the Korean Peninsula.” While the reports — some relying on satellite imagery predating the summit — haven’t been verified, they suggest Secretary of State Mike Pompeo has much to discuss during his trip to Pyongyang.

“The reports are just a good reminder of how complicated and difficult it is to denuclearize the North,” said Shin Beomchul, director at the Asan Institute for Policy Studies’ Center for Security and Unification. “North Korea’s intent to denuclearize has been verified only by words and, now with Pompeo expected to make another visit to Pyongyang, it’s time to prove them with actions.”

Since the summit, Kim has expanded ties with rivals and allies, visiting China and holding talks on economic cooperation with South Korea. Trump has touted the agreement in rallies despite criticism by arms-control experts that the lack of a clear ­implementation framework makes it easy for Kim to exploit.

Meanwhile, the U.S. and South Korea have suspended regular military exercises seen in North Korea as a threat.

Although Kim has pledged to halt nuclear-weapons tests and demolished a facility used for all six of the nation’s atomic bomb detonations, he has said nothing about production and made no commitment to unilaterally disarm. U.S. defense analysts have said North Korea retains as many as 60 nuclear bombs and a range of missiles, including some that are capable of striking the U.S.

Recent revelations include an NBC News report that said U.S. intelligence agencies believe North Korea has increased its production of enriched uranium fuel for nuclear weapons at multiple secret sites in recent months.

That undercuts Trump’s own rosy take after the summit. “President Obama said that North Korea was our biggest and most dangerous problem. No longer — sleep well tonight!” he said in a June 13 tweet.

Moreover, the Middlebury Institute of International Studies released an analysis Sunday that found North Korea has recently expanded a factory complex in the eastern city of Hamhung that produces key engines for solid-fuel ballistic missiles. The construction came after Kim made a similar “denuclearization” pledge during his April 27 meeting with South Korean President Moon Jae-in.

The factory in question produces wound-filament airframes and nozzles for engines used in solid-fuel missiles, particularly the Pukguksong series of rockets, the report said. Such missiles are more concerning to U.S. military planners because they can be kept hidden while fueled, making them easier to deploy and harder to target in any attack.

“The expansion suggests that, despite hopes for denuclearization, Kim Jong Un is committed to increasing North Korea’s stockpile of nuclear-armed missiles,” the report’s authors David Schmerler and Jeffrey Lewis wrote.