North Korea will top US Secretary of State Mike Pompeo’s agenda as he heads to an Asian security meeting in Singapore this week amid new concerns over Pyongyang’s ballistic missile program and commitment to denuclearisation.

Mr Pompeo and North Korea’s foreign minister are both set to attend the annual Association of Southeast Asian Nations Regional Forum on Saturday and US officials say a meeting between the two of them is possible, although not confirmed.

North Korea is one of 27 members of the forum, which in the past has served as a venue for meetings between top diplomats from Pyongyang and Washington.

Singapore was also the site of last month’s historic summit between President Donald Trump and North Korean leader Kim Jong Un at which the two reached a loose agreement on denuclearisation.

North Korea “will be in the room and there will certainly be discussions about denuclearisation,” one senior State Department official said.

Since the Trump-Kim summit though, issues have arisen to give US and other analysts pause.

On Tuesday, the Washington Post reported US intelligence officials suspect North Korea is continuing to build new missiles in the same research facility that manufactured the country’s ballistic missiles capable of reaching the United States.

The Post also reported that North Korean officials have talked about how they plan to deceive the US about the size of their arsenal of missiles and nuclear warheads and facilities.

“Their strategy includes potentially asserting that they have fully denuclearised by declaring and disposing of 20 warheads while retaining dozens more,” the newspaper said.

Missile experts, using open source satellite information, also reported seeing activity at the research facility in Sanumdong near the capital, Pyongyang.

Jeffrey Lewis, who directs the East Asia Nonproliferation Program at the James Martin Center for Nonproliferation Studies, said his group has reviewed 40 high-resolution images since January.

Intelligence agencies likely have more detailed images, he said, adding in a phone interview: “We’ve tracked the vehicle traffic in and out and it’s still active.

“That facility is used for producing missiles and space launchers and that facility has remained active all year long. There’s new construction and shipping containers going in and out.”

The senior State Department official would not address the report, but Mr Pompeo and other members of Mr Trump’s national security team have cautioned the process of denuclearising North Korea and eliminating the threat from its long-range missiles will not be quick.

They have urged patience even as Mr Trump himself has played up positive developments, including the return of apparent remains of more than 50 American troops killed during the Korean War.

The officials cited by the Post said new evidence, including satellite photos taken in recent weeks, suggests that work is underway on at least one and possibly two liquid-fueled intercontinental ballistic missiles at a research facility in Sanumdong on the outskirts of Pyongyang.

The report cast further doubt on Mr Trump’s claims of victory last month in disarmament talks with North Korea, having declared on Twitter after meeting Mr Kim: “There is no longer a Nuclear threat from North Korea.”

White House counselor Kellyanne Conway on Tuesday played down the significance of the Post report.

“It suggests that this is a process,” she told Fox News of US efforts to denuclearise North Korea.

“Things don’t change overnight.”

Mr Trump asserted last week that his administration’s plan to dismantle North Korea’s nuclear weapons is “going very well”.

He made his remarks after the North Korea-focused 38 North website released recent satellite imagery that seems to show dismantlement underway at Sohae.

But his comment seemed at odds with Mr Pompeo, who said any such step would have to be confirmed by international inspectors and that North Korea continued to produce fuel for nuclear weapons despite Kim’s pledge to denuclearise.

Mr Pompeo said there was “an awful long way to go” before North Korea could no longer be viewed as a nuclear threat.