Four years ago this weekend, then-Secretary of State Madeleine K. Albright visited North Korea, in what appeared to be a breakthrough in U.S. relations with the reclusive Stalinist government. Today, Secretary of State Colin L. Powell leaves on what may be his last official visit to East Asia -- hopping through Japan, China and South Korea over three days -- with the crisis over North Korea's nuclear ambitions at the top of his agenda.

Since President Bush took office four years ago, a deal to keep North Korea's nuclear materials under international inspection collapsed -- after the administration discovered a clandestine nuclear program -- and the government in Pyongyang appears to have produced enough weapons-grade plutonium to build at least six more nuclear weapons. Meanwhile, senior members of the Bush administration have been deeply split over its policy toward North Korea, limiting U.S. diplomatic flexibility.

Powell, despite misgivings by other senior officials, who wish to confront and isolate North Korea, has tirelessly promoted a six-nation negotiating track. But the talks appear to have reached a stalemate, with North Korea refusing to attend another meeting -- at least until after U.S. presidential election yields a winner.

Powell's trip, his first in the region in 18 months, represents an effort to convince allies that the Bush administration is committed to a negotiated approach, even in a second term. Powell does not appear to be bringing a new proposal, but he clearly hopes that other countries in the region, such as China, will prod North Korea to return to the negotiating table before the momentum of the talks, last held in June, dissipates.

The Bush administration's handling of the North Korean threat was the subject of sharp exchanges during the first presidential debate, with Democratic challenger John F. Kerry harshly criticizing Bush for allowing North Korea to become more dangerous while he was preoccupied with Iraq. For Powell, North Korea has been the Moby Dick of foreign policy, with his preferred approach often tempered by his detractors in the president's Cabinet.

On North Korea, "I would say the administration has constructed a railroad track headed for a cliff," said Charles "Jack" Pritchard, until August 2003 Powell's special envoy for the North Korea talks. "The train is going down a steep slope, 80 miles an hour, and Powell has gotten the train down to 40 miles an hour. But it's still going off a cliff."

During the first presidential debate, Kerry noted that in the early months of the Bush administration, Powell suggested that Bush would follow the approach of the Clinton administration, which believed that it had been close to a deal limiting North Korean missiles. But "the president reversed him publicly," Kerry said, leaving the president of South Korea "bewildered and embarrassed."

The episode was indicative of the conflicting signals the Bush administration has sent about its policy toward North Korea.

In April, Vice President Cheney visited the region and told an audience in Shanghai that "time is not necessarily on our side." He asserted that North Korea, given its past behavior, could peddle nuclear technology to terrorist groups. Moreover, he warned that, as North Korea's neighbors face the reality that it has a stockpile of nuclear weapons, "we [may] have a nuclear arms race unleashed in Asia."

While Cheney expressed clear frustration with the pace of diplomacy, Powell said this week that "this is an area where you have to have patience and determination."

Aides close to Powell insist that, notwithstanding interagency squabbles, the president has privately made it clear that he supports a diplomatic approach. Powell said that publicly this week, in a Far Eastern Economic Review interview released yesterday. "All I know is what the president has decided," he said. "And he's the only one I'd listen to. And he's decided this: He's decided it repeatedly over the last year that we would try to solve this diplomatically."

Powell added: "We'll have to be patient. We will not change our policy."

While Bush had initially blocked talks with North Korea after he came into office, U.S. officials reached a consensus in early 2002 that representatives of the two countries should meet. But over the summer of 2002, U.S. intelligence determined that North Korea had a secret program to enrich uranium, in violation of a 1994 deal to freeze its nuclear programs, which had been reached with President Bill Clinton.

That discovery ended the prospect of any improvement in U.S.-North Korean relations. Bush's foreign policy advisers quickly agreed that the discovery amounted to a "material breach" of the 1994 deal, and that they needed to confront the North Koreans.

During an October 2002 meeting with U.S. officials in Pyongyang, North Korea unexpectedly acknowledged the clandestine program. The United States cut off deliveries of fuel oil provided under the 1994 agreement, and in response, North Korea kicked out international inspectors and restarted a nuclear facility that had been shuttered by Clinton's deal -- giving Pyongyang access once again to a key ingredient of nuclear weapons.

Democrats have charged the Bush administration with dropping the ball by allowing North Korea to produce the weapons-grade plutonium -- an act that Clinton had warned would prompt a military attack. But administration officials say the clandestine program demonstrated that the 1994 agreement was already worthless. "The fact of the matter is that things had deteriorated before this administration came in, but they didn't know it," Powell said in the magazine interview.

The first two rounds of the six-nation talks, held in Beijing, did not produce much movement. In June of this year, the Chinese and the South Koreans began to press for a more concrete U.S. proposal. On June 15, Powell outlined to Bush's senior foreign policy advisers a plan seeking "points of flexibility" in the next round of talks.

Under the proposal, if North Korea agrees to terminate its nuclear programs, South Korea and other U.S. allies could provide immediate energy assistance to North Korea, which would have three months to disclose its programs and have its claims verified by U.S. intelligence. The United States would then join its allies in giving written security assurances and participate in a process that might ultimately result in direct U.S. aid.

Defense Secretary Donald H. Rumsfeld won Bush's approval for one significant change: Powell had proposed to immediately offer security assurances to North Korea as South Korea starts fuel shipments, but instead the security assurances would be offered after the North Korean declaration is verified.

North Korea rejected the offer. In recent weeks, South Korean officials have pressed the United States to modify the proposal to include some sort of symbolic commitment to assisting with the fuel oil shipments, such as paying the administrative expenses. But U.S. officials have opposed that idea.

At the State Department, Secretary of State Colin L. Powell receives Yoon Kwang Ung, South Korea's defense minister, on the eve of a three-day trip to Asia.