The bargain among six nations gives North Korea energy, food and other aid in exchange for shuttering its main nuclear reactor. It does not expressly require the North to give up existing weapons or testing now, and the agreement does not spell out how negotiators will resolve issues that have derailed previous pacts.

President Bush, who once labeled North Korea part of an "axis of evil," said the bargain is a promising first step toward getting rid of the North's nuclear weapons.

"These talks represent the best opportunity to use diplomacy to address North Korea's nuclear programs," Bush said in a cautious statement that stressed North Korea's obligations while saying little about what the United States would do.

Secretary of State Condoleezza Rice repeatedly urged patience.

"This is not the end of the story," Rice told reporters.

Skepticism was wide and criticism swift, focusing on the troubled history of negotiations with North Korea, and on what lessons Iran or any other countries with nuclear programs could draw.

On the right, a former top Bush aide joined conservative commentators in calling the deal Pollyannaish.

Former U.N. Ambassador John Bolton said the agreement rewards North Korea for bad behavior while encouraging Iran to ignore international demands that it roll back its nuclear program and hold out for a better deal.

"I will be the saddest man in Washington" if Bush goes along with the agreement, Bolton told reporters. "I think the agreement is fundamentally flawed."

At the conservative Heritage Foundation, analyst Bruce Klingner said the deal "reflects America's abandonment of several previously intractable negotiating positions. "

North Korean leader Kim Jong-il "used his characteristic mixture of military provocations, brinksmanship and crisis diplomacy to gain benefits for a return to the status quo ante and promises of future steps," Klingner said.

On the left, critics said Bush could have had the same deal years ago if he had not been so rigid in his approach to the North.

"This deal takes us back to the future," said Sen. Joe Biden, D-Del. "The good news is that it freezes in place North Korea's nuclear program. The bad news is that North Korea's program is much more dangerous to us now than it was in 2002, when President Bush rejected virtually the same deal he is now embracing."

Analysts say that at the start of the Bush administration North Korea probably had enough material to build one or two weapons, and now probably could produce at least 10.

North Korea stunned the world when it set off an underground nuclear test last October, proving its claim to possess weapons. The North also test-fired a long-range missile last summer, showing that it has the theoretical ability to deliver nuclear weapons as far as the U.S. West Coast.

"The deal announced today essentially freezes the North Korean weapons program, but it does nothing to actually force the country's leaders to give up any of the gains they've made in recent years," Sen. John Kerry, D-Mass., said. "Unless the Bush administration continues to engage North Korea and stays focused on working diplomatically to find long-term solutions, we are likely to be dealing with this issue again in 12 months."