Russia launched a mission Thursday to try to bring North Korea back into international disarmament talks, sending its top diplomat to Pyongyang after the North announced it would restart its nuclear program.

Foreign Minister Sergey Lavrov arrived in North Korea for a two-day visit, the official Korean Central News Agency reported in a brief dispatch. Russia's ITAR-Tass news agency said the nuclear standoff was expected to dominate Lavrov's trip, and that he might meet later Thursday with leader Kim Jong Il.

North Korea last week expelled all international monitors of its nuclear facilities, vowed to restart them and quit six-nation disarmament talks, after the U.N. Security Council condemned its April 5 rocket launch and called for expanded sanctions.

North Korea says the rebuke is unfair because the liftoff was a peaceful satellite launch. But the U.S. and others believe it was a test of long-range missile technology.

International Atomic Energy Agency chief Mohamed ElBaradei said earlier this week that the North could restart its nuclear facilities within months, which would allow it to produce weapons-grade plutonium.

South Korean and Russian media reports said Lavrov was expected to deliver a letter from Russian President Dmitry Medvedev.

Lavrov met Thursday with North Korean Foreign Minister Pak Ui Chun, ITAR-Tass reported. KCNA said he signed a culture and science exchange agreement with North Korea and paid his respects at the palace where the embalmed body of North Korea founder Kim Il Sung is displayed.

North Korea's relations with Moscow are not as close as they were during Soviet times, but are cordial. Moscow is a participant in the six-party nuclear talks and usually avoids openly criticizing the North.

"A threat of sanctions to North Korea is counterproductive," ITAR-Tass quoted Lavrov as saying, without specifying the time or place of his comments.

He also said all the parties in the nuclear talks should stick to their obligations. "There are commitments taken by North Korea and there are commitments taken by the other participants in the six-way talks," Lavrov said, according to ITAR-Tass.

Under a 2007 six-party deal, North Korea agreed to disable its main nuclear complex in Yongbyon north of Pyongyang in return for the equivalent of 1 million tons of fuel oil and other concessions. In June 2008, North Korea blew up the cooling tower there in a dramatic display of its commitment to denuclearization.

But the disablement came to halt a month later as North Korea wrangled with Washington over how to verify its past nuclear activities. The latest round of talks, in December, failed to push the process forward.

South Korean Foreign Minister Yu Myung-hwan warned the North of consequences if it restarts its nuclear facilities.

"It would mean greater risk of North Korean proliferation," Yu told reporters. "I think corresponding measures will be taken not only by the United Nations, but also by related countries, including South Korea and the U.S."

In Washington, Secretary of State Hillary Rodham Clinton told a House hearing that Washington is ready to resume the nuclear talks and that she thinks the "strong support that we see among the parties against what North Korea is doing will eventually yield fruit."

"We have to be strong, patient, persistent, and not give in to the kind of back-and-forth ... the unpredictable behavior of the North Korean regime," Clinton said.

Lavrov also plans to visit South Korea on Friday after the North Korean trip.

Tensions on the divided peninsula have also been running high. The two sides held their first official dialogue Tuesday since Seoul's conservative President Lee Myung-bak took office last year, but the brief meeting ended without progress.

North Korea rejected Seoul's request for the release of a South Korean worker being held at a joint industrial zone in Kaesong, just north of the border, for allegedly denouncing the North's political system. North Korea also demanded that South Korean companies pay more to use the factory park.

Relations between the two Koreas have frayed badly as North Korea has denounced the South Korean government's tougher stance. It cut off reconciliation talks and suspended key joint projects, leaving the industrial zone as the only major remaining project.