South Korea (searchtried to bolster hopes for a breakthrough in the North Korean (searchnuclear crisis Thursday, confirming China had delivered a pivotal U.S.-backed plan for easing tensions to North Korea.

The United States, Japan and South Korea presented a blueprint for ending the standoff to China, which is playing the role of mediator, earlier this week but a report Wednesday said Beijing (search) found the plan unacceptable and never bothered relaying it.

"I checked this morning and confirmed that it has been delivered to North Korea," said South Korea's Unification Minister Jeong Se-hyun, adding that he was still hopeful six-nation talks to resolve the nuclear crisis could be held soon.

Jeong also said he could not confirm reported activities at North Korea's main nuclear facility in Yongbyon.

South Korea's major JoongAng Ilbo newspaper reported that a U.S. intelligence satellite spotted vapor and fumes coming from the nuclear site, and that Washington and Seoul were trying to analyze whether Pyongyang was reprocessing spent fuel rods to extract weapons-grade plutonium.

"I do not have information at this point to say anything definitely," Jeong said.

North Korea previously claimed that it had reprocessed all of its 8,000 spent fuel rods -- a key step in making atomic bombs. U.S. officials believe North Korea already has one or two nuclear bombs.

The North Korean nuclear crisis flared in October last year, when U.S. officials said the communist state admitted running a new nuclear weapons program using enriched uranium in violation of international agreements.

North Korea says its has restarted its frozen 5-megawatt reactor at Yongbyon, 50 miles north of Pyongyang, after it kicked out U.N. nuclear inspectors and quit the Nuclear Nonproliferation Treaty in January. Experts have said it would take a year of operation before the reactor can produce enough to make a new weapon.

The United States and its allies seek to persuade North Korea to end the nuclear programs through the six-nation talks.

The United States, China, the two Koreas, Japan and Russia held the first meeting in August, but made little progress. Pyongyang has said it won't join a second round of talks until its demands are met.

Details of the U.S.-backed proposal were unclear, but media reported that it seeks the complete, verifiable and irrevocable dismantling of the North's atomic weapons program and security assurances for Pyongyang.

North Korea offered Tuesday to freeze its nuclear weapons activities if the United States provided energy aid and removed Pyongyang from a list of countries that sponsor terrorism, but Jeong said it wasn't clear if that was in response to the U.S. proposal. President Bush rejected the offer.

North Korea said it was responding to "what is now afloat and what we hear" and that it was disappointed in the U.S. stand.

Jeong was hopeful about the possibility of a second-round of six-nation over North Korea's nuclear weapons programs this month.

"North Korea is saying that it will make those demands when the talks open. I think North Korea is expressing its strong willingness to hold talks," he said. "I think there is still hope."