"There are people suggesting that perhaps there will be a rollout of a new weapon system," Abrams said at a conference organized online by the Center for Strategic and International Studies (CSIS) in Washington.

"Maybe, but we're not seeing any indications right now of any sort of lashing out," he added, noting that Pyongyang is grappling with the aftermath of Typhoon Maysak, international sanctions and the coronavirus pandemic.

CSIS published on its website a satellite image of North Korea's Sinpo South naval shipyard, which its experts believe shows activity that could indicate possible preparations for a test of a submarine-launched ballistic missile.

A new North Korean missile test would be yet another sign of the lack of progress in denuclearization talks between the US and Pyongyang, which have been stalled despite multiple meetings between Kim and President Donald Trump.

Trump, who is seeking reelection in November, was the first sitting US leader to meet a member of the Kim dynasty, which has ruled North Korea since its founding.

On Thursday, Trump tweeted, without further explanation: "Kim Jong Un is in good health. Never underestimate him!"