The US has dismissed demands from North Korea to have sanctions against it lifted as a precondition for returning to the talks on its nuclear programme.
Pyongyang test-fired seven missiles on Wednesday
US envoy Christopher Hill accused the North of trying to divert attention from its "reckless" missile tests.
But he said he supported a Chinese plan for informal six-party discussions to try to re-engage the North Koreans.
Mr Hill is on a tour of the region to co-ordinate a response to the missile tests held by North Korea on Wednesday.
The country drew worldwide condemnation for test-firing seven missiles, including a long-range Taepodong-2 - believed to be capable of reaching Alaska.
The missiles failed and fell into the Sea of Japan.
On Saturday, a new American warship reached its base in Japan.
The guided missile destroyer USS Mustin will be based in Yokosuka. Its radar can track ballistic missiles like North Korea's Taepodong.
Speaking after meetings in Seoul with South Korean officials on Saturday, Mr Hill said the US would not lift financial sanctions to bring the North back to negotiations.
"This is not a time for so-called gestures of that kind," he said.
"We have a country that has fired off missiles in a truly reckless way, that affect the regional tranquillity and indeed affect regional security."
Mr Hill also urged the north to "come to the six-party process".
Negotiations involving the two Koreas, Russia, China, Japan and the US have been stalled since November.
Mr Hill, however, said he supported China's offer of hosting informal six-way talks.
He added that if the round was arranged, he would be willing to meet North-Koreans bilaterally on the sidelines.
Meanwhile Japan has presented a draft resolution to the UN Security Council, calling for sanctions against North Korea.
It urges North Korea to immediately stop developing, deploying and testing ballistic missiles and to return to talks on its nuclear programme.
Japan, with co-sponsors the US, Britain and France, want the council to decide on Monday when a vote will take place.
Sanctions are opposed by Russia and China, which have veto powers in the security council.
North Korea's deputy envoy to the UN, Han Song-ryol, has reportedly said any UN sanctions would be "an act of war".
South Korea has suspended its shipments of food aid to the North until the situation over the missile-testing is resolved, officials said.
South Korea is the North's biggest food aid donor, helping the impoverished North feed its people.
However, Seoul says it still intends to go ahead with cabinet-level talks scheduled for next week.