The chief U.S. envoy praised the development as a "win-win situation" and "good agreement for all of us." But he promptly urged Pyongyang, which also agreed to international inspections, to make good on its promises by ending operations at its main nuclear facility at Yongbyon.
"What is the purpose of operating it at this point?" said Assistant Secretary of State Christopher Hill. "The time to turn it off would be about now."
Despite the deal's potential to help significantly ease friction between the North and the United States after years of false starts and setbacks, Hill remained cautious.
"We have to see what comes in the days and weeks ahead," he said.
A seeming road bump came later as North Korea refused on Tuesday to dismantle its nuclear weapons program until the United States gives it light-water reactors for power generation.
The North's Foreign Ministry made the statement a day after it agreed at six-nation talks in Beijing to give up its nuclear programs, rejoin the nuclear Non-Proliferation Treaty, and accept inspections by the International Atomic Energy Agency.
"The U.S. should not even dream of the issue of (North Korea's) dismantlement of its nuclear deterrent before providing LWRs, a physical guarantee for confidence-building. This is our just and consistent stand as solid as a deeply rooted rock," the Foreign Ministry said in a statement carried by the North's official Korean Central News Agency.
It also said it would not rejoin the non-proliferation treaty or sign a safeguards agreement with the IAEA until it receives the light-water reactors.
The North's position is likely to be a major sticking point in talks slated to begin in November on implementing Monday's agreement.
President Bush called it a positive step, but he expressed some skepticism about whether North Korea will live up to its promises.
"They have said — in principle — that they will abandon their weapons programs," Mr. Bush said. "And what we have said is, 'Great. That's a wonderful step forward.' But now we've got to verify whether that happens."
"The question is, over time will all parties adhere to the agreement," Mr. Bush said.
The agreement clinched seven days of talks aimed at setting out general principles for the North's disarmament. Envoys agreed to return in early November to begin hashing out details of how that will be done.
Then, the hard work of ensuring compliance will begin, officials attending the talks said.
"Agreeing to a common document does not mean that the solution to our problems has been found," said Japan's chief envoy, Kenichiro Sasae.
Another Japanese official, who spoke on condition he not be named in order to discuss the issue more freely, noted that there was no common understanding among the participants about the nature of North Korea's nuclear program.
"There still is a lot of negotiating that will have to be completed in November, including the specifics of the agreements and time frames," said CBS News foreign affairs analyst Pamela Falk. "But in essence, North Korea has agreed to end its existing nuclear weapons and ongoing development and to include inspections in exchange for a U.S. agreement not to invade or attack North Korea and to gradually normalize relations."
Falk said the agreement also "takes the pressure off the United Nations with regard to North Korea and avoids a contentious debate about sanctions at a time when talks with North Korea had stalled."
The head of the U.N. nuclear nonproliferation agency welcomed North Korea's decision to allow inspections, saying he hoped his experts could take the country at its word as soon as possible.
"The earlier we go back, the better," said Mohamed ElBaradei, head of the International Atomic Energy Agency.