On Wednesday, Mr. Trump threatened to rain down "fire and fury like the world has never seen" if North Korea did not curb its nuclear programs.
Asked whether Mr Trump's escalating rhetoric was hurting prospects for reviving negotiations, Mr Rycroft said: "What's hurting the six-party talks is the inability so far of the North Korean regime to do what it has to do which is to halt its nuclear programme and to halt its intercontinental ballistic missile programme".
One U.S. military official speaking to NBC spoke of the concern that a pre-emptive attack against the DPRK would result in a response, putting people in South Korea at potential risk.
In response to that "fire and fury" threat, North Korea said its military is preparing to conduct a test firing of four missiles that would fly over Japan and land in waters near the USA territory of Guam.
The president's public comments "undermine anyone in Pyongyang who's interested in seeing if there's something to be gained in a dialogue with the United States", he said.
A new report says Pyongyang's nuclear programme is progressing.
B-1 bomber planes have carried out a series of 11 practice runs on the Korean peninsula near the DPRK's border, in coordination with South Korean and Japanese forces since the end of May. We call on the relevant parties to be cautious with their words and actions, and contribute more toward easing tensions and enhancing mutual trust, ' Geng said in a statement.
The Northern Viper drills are one of the scheduled exercises that Japan's Self Defence Forces conducts regularly with their US counterparts and are not a response to the latest tensions.
"We want to use diplomacy [and] that's where we've been, that's where we are right now and that's where we hope to remain, Mattis said during a press briefing on Thursday".
Mattis said the tragedy of war is well-known and "it doesn't need another characterization beyond the fact that it would be catastrophic".