SEOUL, South Korea -- International efforts to shut down North Korea's nuclear program took a surprise turn Thursday when the United States altered course, sending a key American official to Pyongyang for direct talks with the communist country.

Assistant secretary of state Christopher Hill, Washington's chief nuclear envoy to North Korea, was the highest-level U.S. official to visit the North Korean capital since October 2002.

The Bush administration initially preferred to meet the North with regional powers like China and Japan at the talks. But the United States has been moving away from that limitation, holding meetings on the sidelines of summits and sending White House adviser Victor Cha to Pyongyang earlier this year. Hill's trip is the clearest indication yet of reaching out directly.

The visit, coming before North Korea makes good on its promise to shut down its nuclear reactor, appeared to demonstrate how much the Bush administration wants to achieve a breakthrough in the effort to dismantle the Pyongyang regime's atomic weapons program.

"We hope that we can make up for some of the time that we lost this spring, and so I'm looking forward to good discussions about that," said Hill, who went to Pyongyang after several days of discussions with officials in China, Japan and South Korea.

"We want to get the six-party process moving," Hill said in Pyongyang. He referred to talks involving North and South Korea, China, Japan, Russia and the U.S. aimed at securing North Korea's denuclearization in exchange for economic and energy aid for the impoverished state.

APTN footage showed a beaming, relaxed-looking Hill arriving at Pyongyang's airport, where North Korean officials greeted him in just as amicable a manner, readily holding out an umbrella to protect him from a steady downpour.

"We're all waiting for you," said Ri Gun, North Korea's deputy nuclear negotiator. Hill replied that he "got the message on Monday, and we had to work fast to find an airplane."

His remarks suggested the visit was hastily arranged and came in response to a North Korean invitation.

The official Korean Central News Agency reported Hill's arrival in a terse, one-line dispatch. State television did not mention the trip on its evening broadcast.

Hill was to meet with Vice Foreign Minister Kim Kye Gwan, North Korea's lead negotiator in the six-nation talks, the State Department said. He planned to return to South Korea on Friday.

In Washington, the State Department said Hill's trip signaled it was the "right moment to do the full range of face-to-face consultations" with North Korea and to talk about moving the stalled process forward.

Spokesman Sean McCormack had no details on Hill's meetings, which he said were prompted by Kim issuing an invitation to Hill. The spokesman said Hill was not carrying any letters or messages from President Bush or Secretary of State Condoleezza Rice.

McCormack dismissed suggestions that Hill's trip could give the impression that North Korea had the upper hand in the nuclear negotiations or signaled a new direction in U.S. policy. "We're not coming unmoored from our principles or policies," he told reporters.

President Bush, who angered North Korea by including it in his "axis of evil" troika in 2002, agreed the following year to U.S. participation in disarmament talks with the North only if other nations joined in, particularly Pyongyang's lone ally, China.

U.S. officials had previously rejected one-on-one diplomacy to avoid delivering North Korea a perk it sought, which indicates Hill's trip is a vote of confidence in Pyongyang's sincerity about keeping its promises under the six-nation deal.

The U.S. and North Korea have been at odds since the 1950-53 Korean War and do not have formal diplomatic relations. The highest-ranking U.S. official to visit North Korea was then-Secretary of State Madeleine Albright in 2000. Hill's predecessor as nuclear envoy, James Kelly, visited in October 2002.

In February, North Korea committed itself to shut down its main nuclear fuel processing facility, the Yongbyon reactor, by mid-April after the U.S. promised to free $25 million in allegedly illicit North Korean funds.

Enough progress had been made by Saturday for North Korean state media to announce that the country had invited the U.N. nuclear watchdog agency to send inspectors for a visit next week to discuss details of the reactor shutdown.

North Korea, which carried out its first nuclear test explosion in October last year, expelled International Atomic Energy Agency inspectors in 2002.

Hill said Tuesday that the money had finally been deposited in a North Korean bank account in Russia and that the case was closed.

However, a North Korean diplomat in Vienna, Austria, where the IAEA is based, cast doubt on that Thursday, saying the inspectors' trip could be delayed.

"The visit date of the delegation is not confirmed because the release of the frozen funds of the DPRK at Banco Delta Asia in Macao has not been completed," Hyon Yong Man, an official at the North Korean Embassy in Vienna, said in a statement, referring to his country by the abbreviation of its official name.

In Moscow, Russian Deputy Foreign Minister Sergei Kislyak suggested the transfer had begun. "The money is being transferred right now as we are talking," he said. "Everything is normal, all agreements have been reached."

Despite promises by North Korea, the six-party process, which began in August 2003, has failed to achieve any concrete action by the country toward denuclearization.

South Korea's envoy to the nuclear talks, Chun Yung-woo, welcomed Hill's trip.

"It is good news," Chun told The Associated Press. "North Korea's invitation itself is a positive sign of keeping alive the momentum of the six-way talks."

Hill said this week that he hoped the six-nation talks could reconvene sometime after July 4. China, which sponsors the meetings, said Thursday that no date had been fixed. The Chinese foreign minister is to visit North Korea on July 2-4.

"I think the U.S. is trying to keep North Korea from dragging its feet any longer," now that the banking row is resolved, said Nam Sung-wook, a North Korea expert at Korea University. "Unless something is done right now, North Korea could stall for time on another pretext."

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Associated Press writers Jae-Soon Chang and Kwang-Tae Kim in Seoul, Anita Chang in Beijing and Anne Gearan in Washington contributed to this report.