The two main protagonists of the 20-month impasse held a rare two-hour meeting on the sidelines of six-party talks here, but they remain poles apart.
"I cannot characterise what happened in the meeting but I can confirm the meeting took place," a US embassy official said.
While attempting to put a positive spin on the standoff, both Japan and South Korea acknowledged that it was a work in progress.
"As for the issue of uranium enrichment, I think the two sides do not seem to agree at all," Japan's Chief Cabinet Secretary Hiroyuki Hosoda said in Tokyo.
In Beijing, South Korea's deputy chief negotiator Cho Tae-Yong said there were "significant differences between the United States and North Korean proposals".
Both North Korea and the United States have tabled documents here as they look to break the stalemate reached in 2002 when the US said Pyongyang acknowledged it was developing nuclear weapons, violating a 1994 international agreement.
Despite the gulf separating the two nations, Cho said: "It was the first time for concrete plans to come out.
"Given the way the morning session proceeded, substantial discussions will likely continue tomorrow. We have taken an important first step."
Without commenting specifically on the North Korean response to the US proposal, Chinese foreign ministry spokeswoman Zhang Qiyue said "various parties have treated the plans put forward by other parties in a forward looking manner".
For its part, China called the US package "full and comprehensive".
"The plan itself shows that the meeting is progressing and that the US side hopes to see the settlement of the issue," said Zhang.
The US plan, coordinated with China, South Korea and Japan, is seen as more flexible than previous demands for North Korea to first completely dismantle its nuclear programmes before any aid is channeled to the impoverished state.
Under the proposal, North Korea would receive food and energy assistance and a multilateral security guarantee if it agrees to take apart its plutonium and uranium weapons programs.
The United States would also begin direct talks about lifting its array of economic sanctions, and knocking North Korea off its list of terrorist states.
In return, the Stalinist state would have three months to provide a list of its nuclear facilities and allow monitoring.
"A good-faith action on North Korea's part would be met with a good-faith response by the other parties," White House spokesman Scott McClellan said.
It is the first significant overture to Pyongyang since US President George W. Bush took office in early 2001 and branded the North part of an "axis of evil" alongside Iran and pre-war Iraq.
The plan is based on the Libyan model in which Tripoli agreed to shelve its weapons of mass destruction programmes last year.
China, South Korea and Japan had found the previous US stance inflexible and had been in favour of incremental rewards to Pyongyang while it dismantles its nuclear arsenal.
Its success though depends on whether North Korea is prepared to acknowledge and abandon its alleged uranium enrichment facilities, which it has failed to do in two previous rounds of talks .
North Korea has lodged its own 12-page "freeze for compensation" package, including verifiable freezing of its nuclear facilities at the Yongbyon nuclear complex.
Inspections would be permitted, but it was not clear whether a complete dismantling of all facilities would follow.
Analysts said the US presidential elections were weighing heavily on how North Korea behaves.
"(North Korean leader) Kim Jong-il may not take the deal. He may think he can get a better deal from (US presidential candidate John) Kerry," said David Zweig, a China watcher at Hong Kong University of Science and Technology.