BEIJING -- North Korea pledged today to end its nuclear weapons program and rejoin global treaties aimed at stemming the spread of atomic arms in return for energy aid and diplomatic recognition.
"It was a step forward in making this world a more secure place," Bush said. He added, "The question is, over time, will all parties adhere to the agreement?"
According to a joint statement by the six nations involved in negotiations for more than two years, Pyongyang "committed to abandon all nuclear weapons and existing nuclear programs and to return at an early date to the nonproliferation treaty of nuclear weapons." It also said North Korea would accept International Atomic Energy Agency safeguards.
In other matters, the United States and North Korea agreed to respect each other's sovereignty, a key Pyongyang demand, and to take steps to normalize diplomatic relations.
In return for Pyongyang's accord, the other nations agreed that North Korea had the right to the peaceful use of nuclear energy and said they would discuss providing it a light-water reactor in the future.
Pyongyang's demand for a civilian nuclear energy program has been a major stumbling block in this seven-day round of talks. The United States remains fearful that North Korea might divert spent nuclear fuel to weapons -- a step the communist nation is believed to have taken in the past.
Washington affirmed that it had no nuclear weapons on the Korean peninsula and no intention of attacking North Korea, which the Bush administration has in the past characterized as a member of an "axis of evil" and as an "outpost of tyranny."
The announcement marked the first time in the lengthy negotiations that any agreement had been announced. Details are still to be worked out, and the parties agreed to hold another round of talks in Beijing in November.
"This is real progress, and a big achievement," said Zhang Liangui, a North Korea expert at the Central Party School in Beijing. "It's a milestone."
That said, as always with North Korean negotiations, a lot will depend on the details and implementation, a concern Liangui acknowledged.
"It's crucial that the wording won't leave much room for different parties to read different things into it," he said.
On the issue of the reactor, the United States had argued that Pyongyang did not need a civilian light-water reactor, given an offer by South Korea to transmit electricity across its border with the North.
North Korea had also refused to budge. It appeared that the six parties involved -- China, Japan, the two Koreas, Russia and the United States -- finessed this issue by agreeing that North Korea has the right to a peaceful nuclear energy program, as long as it does not exercise that right before safeguards are in place.
At that point, the parties could discuss the light-water reactor.
The United States also affirmed in the statement that it has no nuclear weapons on the Korean peninsula and no intention of attacking or invading North Korea.
All six nations agreed to promote cooperation in the fields of energy, trade and investment.
The fourth round of talks followed what has become a familiar pattern in tortuous negotiations with North Korea, with a breakthrough coming just as it seemed the negotiators were about to throw up their hands and walk away. Earlier in the day, Assistant Secretary of State Christopher Hill, the chief U.S. negotiator, described the talks as at an "endgame," and the parties as ready to go home.
The key sticking point had been what type of civilian nuclear program North Korea would be allowed to keep after dismantling its weapon-making facilities. The United States readily acceded to Pyongyang's demands to use a small research reactor to produce radioactive isotopes for medicine and agriculture, but vetoed the idea of a light-water reactor -- a type less easily adapted to weapons production -- for electricity.
The parties got around this hurdle by agreeing to "discuss at an appropriate time" the building of a light-water reactor for North Korea, according to the statement.
Under a now-collapsed 1994 deal, a U.S.-led coalition was building twin light-water reactors for North Korea. But the Bush administration pulled the plug on the deal in 2003 after North Korea was caught cheating on its disarmament agreements. The nearly $5 billion project is about one-third completed.
A new proposal that has the United States' endorsement calls for South Korea to run what would be in essence a large extension cable across the demilitarized zone. Under the proposal that South Korea reaffirmed at this week's talks, North Korea would get 2 million megawatts of electricity -- exactly the same amount as through a light-water reactor -- through conventional means, with the advantage of it being technically quicker and easier to complete.
But the North Koreans have balked at the idea of being dependent for their electricity on arch-rival South Korea. The mountainous North has abundant natural resources of uranium, the fuel for light-water reactors, and wants to be energy self-sufficient.
Making their case, the North Koreans have pointed to language in the Nuclear Nonproliferation Treaty's Article IV, which upholds "the inalienable right of all parties to the treaty to develop research, production and use of nuclear energy for peaceful purposes without discrimination."
North Korea announced it was withdrawing from the treaty in late 2002, but now proposes to return to it.
Much of the recent wrangling has had to do with whether the North Koreans could be acknowledged to have a theoretical right to a civilian nuclear program, without actually obtaining a light-water reactor. Several compromises have been proposed under which Pyongyang would gradually build back the trust of the international community to the point that it might be allowed to have a reactor.
Although it has received the most attention recently, the peaceful use of nuclear power is not the only sticking point. The Bush administration wants a far more extensive nuclear dismantlement than occurred after the 1994 treaty. North Korea is expected not only to dismantle its plutonium-based weapons program at Yongbyon, the country's main nuclear facility 60 miles north of Pyongyang, but also a secretive nuclear program based on highly-enriched uranium. It was news of the existence of this program in late 2002 that caused the earlier treaty to collapse.
North Korea had denied having a highly-enriched uranium program, and some other parties to the talks, notably China and Russia, have expressed doubts about the Bush administration's evidence.
In addition, North Korea will be forced to account for and dismantle its already-completed nuclear bombs, possibly as many as 13, which are believed to be hidden underground throughout the country.
Today's agreement skirted many of these difficult issues, which are likely to raise considerable hurdles in the next round of talks scheduled for November.
Last-minute pressure and the threat of a deadline appeared to push the deal through. Hill had already announced that he was leaving town and had scheduled a news conference.
Early this morning, however, China and the United States reportedly met again before the group of six nations reconvened, leading to the announcement of a deal in the early afternoon.
China was very keen to see this round produce some sort of results. A failure of this, the fourth rounds of talks in two years, would have threatened the talks as an approach. China viewed its role as host of the talks as an important element in its growing international profile.
The United States has in the past threatened to pursue United Nations sanctions against North Korea if discussions dragged on too long.
The U.S. threat has been tempered somewhat, however, by practical considerations.
Applying economic pressure on the impoverished and isolated Stalinist state could be difficult. Both of the North's closest neighbors, which are also its largest trading partners, China and South Korea, have opposed the use of sanctions, fearful that they might only strengthen North Korea's resolve and lead to a flood of refugees.
Pyongyang has also said that any use of sanctions amounted to a declaration of war.
Demick reported from Seoul and Yin Lijin in The Times' Beijing bureau contributed to this article.