In a message aimed at both Koreas, a senior U.S. diplomat said Wednesday that Washington is open to settling the North Korean nuclear standoff through diplomacy, but only if Pyongyang improves ties with archrival South Korea.

The comments by Assistant Secretary of State Kurt Campbell, the top U.S. diplomat for East Asia, were a signal to North Korea's new government that Washington is ready to talk after weeks of transition and uncertainty following the Dec. 17 death of longtime leader Kim Jong Il.

But Campbell also looked to reassure worried allies in Seoul that diplomacy will progress only as long as South Korea is satisfied with North Korea's stance. North Korea has vowed since Kim's death not to deal with South Korea's current conservative government, but it has also suggested a willingness to negotiate with the United States.

"We are open to diplomacy with North Korea, but there is a very clear set of steps that we think are necessary," Campbell told reporters after meetings with South Korean Deputy Foreign Minister Kim Jae-shin and South Korean nuclear envoy Lim Sung-nam.

"We agreed that the path is open to North Korea toward the resumption of talks and improved relations" with Washington and Seoul, Campbell said, but "the road to improve these relations runs through Seoul for North Korea."

"We are still waiting to see whether the new government in North Korea is prepared to take the necessary steps," Campbell said.

Many are closely watching to see what direction North Korea will take as Kim's young son, Kim Jong Un, works to consolidate power and extend his family dynasty into a third generation.

North Korea proudly trumpets its efforts to build nuclear weapons and has a history of aggression against its southern neighbor, and there has been uncertainty about whether Pyongyang will now lean toward provocation or reconciliation _ and how tightly Pyongyang will cling to its nuclear program.

Pyongyang conducted nuclear tests in 2006 and 2009 and has developed missiles with the potential to attack its neighbors and possibly reach the United States.

South Korea on Wednesday said Kim Jong Il's death can be an opportunity for positive change in North Korea, despite the heightened uncertainties.

"We urge North Korea to relinquish its attitude of being closed and committing armed provocations, and to follow a path toward both Koreas creating a better future," Unification Minster Yu Woo-ik said at a forum in Seoul, according to his ministry.

Shortly before Kim's death, Washington and Pyongyang appeared close to a deal on food aid. The North, in turn, was expected to suspend uranium enrichment, which could give Pyongyang another possible route to making nuclear bombs and is a crucial hurdle to restarting six-nation aid-for-nuclear disarmament talks that have been stalled since early 2009.

North Korea has repeatedly pressed for the resumption of those nuclear talks, but Washington and Seoul have said Pyongyang must first follow through on previous nuclear commitments.

Campbell urged China, North Korea's only major economic and political backer, to share more of its plans concerning North Korea with Washington and Seoul.

Japan's Tokyo Shimbun newspaper, citing unidentified sources, reported this week that China decided to provide 500,000 tons of food and 250,000 tons of oil to North Korea in a move meant to help stabilize Kim Jong Un's leadership.

Campbell said the United States believes Chinese officials have "taken steps to underscore their commitment to the transition in power in North Korea. Those steps might include further provision of assistance, given the circumstances in North Korea." He didn't elaborate.

North Korea regularly criticizes South Korean President Lee Myung-bak and says it won't work with him. South Korea has cut off large-scale official food aid to North Korea since Lee took office in 2008, saying North Korea should first take steps toward nuclear disarmament.

North Korea has also condemned South Korea's refusal to allow its citizens, except for two private delegations, to visit Pyongyang and pay respects to Kim Jong Il during a mourning period in December.

The poor ties between the rivals also extend to sports. South Korea said Wednesday that a North Korean youth football team boycotted a game in China against a South Korean squad because of the high political tensions.

Still, Pyongyang has also suggested it is open to suspending its uranium enrichment program if it can get the food it wants from the United States.

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Associated Press writers Hyung-jin Kim and Jiyoung Won in Seoul contributed to this story.

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Follow Foster Klug on Twitter at twitter.com/APklug.