U.S., North Korea Reach Nuclear Pact : Foreign policy: Pyongyang pledges not to pursue arms program; Washington agrees to help update reactors. Both move to form diplomatic ties, but more talks are needed.

North Korea pledged early today to stop trying to obtain nuclear weapons, an agreement that apparently defuses the most dangerous foreign policy crisis facing the Clinton Administration and its allies in Asia.

In exchange, the United States agreed to help North Korea modernize its nuclear power facilities, the parties said in a joint statement issued in Geneva. The two nations also agreed in principle to establish diplomatic missions in each other’s capitals for the first time since the internationally isolated, Communist-ruled state was established after World War II.

The agreement, announced at the end of talks that lasted well past midnight, provided a welcome victory for President Clinton one day after he suffered stunning defeats in Congress on crime and health care legislation. Some details of the accord, however, were left to later negotiations, scheduled to begin Sept. 23 in Geneva.

“This is extremely important because it’s one of those foreign policy achievements that takes a lot of work and effort and, in the context of this kind of changing world, is very significant, particularly when you are dealing with a country like North Korea,” White House Chief of Staff Leon E. Panetta said in a telephone interview. “I think this is a real breakthrough.”

The protracted dispute with North Korea had been cited by critics of the White House as further evidence of disarray in the Administration’s foreign policy.

“I don’t think the crisis is over. But it (the agreement) certainly represents a significant step in trying to improve relations,” Panetta said.

South Korea’s Foreign Ministry today hailed the Geneva statement as a move toward “final resolution of the North Korean nuclear problem.”

“It is definitely progress,” said William Clark, a State Department expert on Asia during the George Bush Administration and now a scholar at the Center for Strategic and International Studies in Washington. “It was never going to be a quick fix with the North. . . . What they have done here is put the U.S. offer on the table.”

According to news agency reports from Geneva, North Korea pledged to implement the joint declaration with South Korea on making the Korean peninsula free of nuclear weapons. The Pyongyang government also promised to remain a party to the Nuclear Non-Proliferation Treaty, an international accord designed to stem the spread of nuclear arms.

Clark said that, if North Korea keeps its word, those steps would end its nuclear weapons program. The North-South pact bans both nuclear arms and the fuel-reprocessing facilities that produce weapons-grade plutonium. Under the non-proliferation treaty, North Korea’s nuclear power plants would be subject to international inspection. But North Korea did not agree to unlimited inspections.

In return, Washington said it will give Pyongyang “assurances against the threat or use of nuclear weapons by the United States.” America also agreed to help North Korea modernize its electricity-generating facilities with light-water nuclear reactors.

Such reactors are far more efficient than the graphite-moderated equipment that North Korea now uses. Light-water reactors also produce far less plutonium.

Assistant Secretary of State Robert L. Gallucci, chief delegate to the Geneva talks that began Aug. 5, said he is confident the United States can get together an international consortium to provide the necessary technology and funding for the new technology.

The reactor modernization program, however, will take at least a decade to complete, so North Korea will continue to use its existing facilities well into the next century.

The joint statement said that more negotiations will be required to determine the disposition of about 8,000 spent nuclear fuel rods now corroding in a cooling pond north of Pyongyang.

The latest crisis was touched off in May when North Korea removed the rods from its Yongbyon nuclear plant in defiance of International Atomic Energy Agency regulations.

The rods contain enough plutonium for several nuclear weapons. The United States wants to ship them to a third country, but North Korea has not agreed to that step.

North Korea said it will take measures to stabilize the rods to delay the risk of them giving off radiation and agreed to permit international inspectors to supervise the work. Pyongyang previously had argued that it must begin reprocessing the rods by the end of August or they would start to give off harmful radiation.

The two countries agreed in principle to establish liaison offices in Pyongyang and Washington to provide representation, a step that stops short of full diplomatic relations. But their statement said that further negotiations will be required to work out the details.

Presumably, the liaison office agreement was included as a gesture to Kim Jong Il, North Korea’s new leader. It gives Kim--who took over after the death last month of his father, Kim Il Sung--a measure of international legitimacy that the elder Kim never achieved during almost half a century of power.

The statement also said the two nations will “reduce barriers to trade and investment as a move toward full normalization of political and economic relations”--measures that would ease North Korea’s isolation.

Times staff writer Ronald Brownstein contributed to this report.