U.S. Assistant Secretary of State Kurt Campbell held talks Thursday with South Korean officials in Seoul on how to revive stalled nuclear disarmament negotiations with North Korea following the death of Kim Jong Il.

Campbell met with Lim Sung-nam, South Korea's top negotiator to six-party talks aimed at convincing North Korea to abandon its nuclear program in exchange for economic aid.

Campbell arrived in Seoul Wednesday after spending two days meeting with officials in China. He is expected to meet with South Korean Foreign Minister Kim Sung-hwan before heading to Japan on Friday to wrap up his four-day diplomatic tour.

Japan, China, Russia, the United States and the two Koreas are participants in the six-nation nuclear talks, which Pyongyang abandoned in April 2009.

Earlier this week, South Korean President Lee Myung-bak said he was optimistic that 2012 could be a turning point in the North Korean nuclear dispute. Pyongyang has rejected demands by South Korea and the United States to shut down its uranium enrichment plant and take other steps before returning to the six-party talks.

Meanwhile, the U.S. on Thursday vowed to strengthen defense ties with South Korea. The incoming deputy commander of U.S. forces in South Korea, Lieutenant General Jan-Marc Jouas, said the alliance between Washington and Seoul would grow stronger in the wake of “political instability” caused by Mr. Kim's death.

“As we continue our vitally important mission on the Korean peninsula, we look to a future filled with uncertainty across Asia. The death of Kim Jong Il has added political instability to an already unpredictable North Korean regime.”

He said ties between U.S. and South Korea will continue to deepen based on the “common values of democracy, market economy, and mutual trust” between the American and South Korean people.

On Wednesday, the South Korean Defense Ministry said its government will soon sign a deal with the United States to increase military exercises and boost preparedness in case of a possible North Korean aggression. About 28,500 U.S. troops are currently stationed in South Korea.