In his upcoming summit with North Korean leader Kim Jong-un, United States President Donald Trump is aiming to eliminate the country's arsenal of chemical and biological weapons as well as nuclear ones, the top American envoy to Japan said Thursday.

"We had broad-ranging discussions on the topic and it extended beyond denuclearization to the topics of chemical and biological weapons as well," US Ambassador to Japan Bill Hagerty told a telephone conference with Asian reporters following the two-day summit between Trump and Japanese Prime Minister Shinzo Abe at the Mar-a-Lago resort in Florida.

"President's intention is to see all of these weapons of mass destruction eliminated from the Korean Peninsula and the strategy remains the same in terms of complete, verifiable and irreversible aspects of denuclearization," he said.

His remarks hint that removing chemical and biological weapons may also be under discussion in ongoing preparations between Washington and Pyongyang for the Trump-Kim summit slated for May or early June.

Asked about a US time line for North Korean denuclearization, he declined to directly address the question, but said the US and Japan "have a sense of urgency coming out of these (Trump-Abe) meetings."

The ambassador said that Trump will be more than happy to walk away from his planned summit with Kim if it does not produce any results.

"Let me be clear that a meeting between the two leaders are not an end in itself. President has no interest in having a meeting for the sake of meeting," Hagerty noted. "This is all aimed at making it certain that we have a meeting that is constructive and moving our agenda forward."

If the US has the sense that that's not the case, the president "is not going to waste his time," he said.

"Frankly, he's not interested in allowing more time to pass," he noted, warning that the US will ratchet up diplomatic sanctions and pressure on the North Korean regime in case the meeting does not lead to progress.

"Our hope is that the outreach by the North Korean regime is sincere ... but at the moment, if President feels there is not a sincere desire on the other side or that this will not lead to a constructive outcome, he's more than happy to go out of the discussion," Hagerty said.(Yonhap)