"The desire by the North Koreans to convince the world that they're in the process of developing a nuclear arsenal is nothing new," Mr. Bush said, striking a far more moderate tone than in March, when he declared that the United States would not tolerate a nuclear North Korea.

He insisted that cooperation with China on a diplomatic solution was moving forward and said American allies would work "to convince Kim Jong Il," the North Korean leader, "that his decision is an unwise decision."

Mr. Bush's remarks — which are in sharp contrast to his words and actions regarding Iraq — come at a time when American and Asian officials have said there is "worrisome" but not "conclusive" evidence that North Korea has constructed a second plant for producing weapons-grade plutonium.

Nearly two weeks ago, North Korean officials declared that they had completed reprocessing 8,000 spent nuclear fuel rods, enough to make about a half dozen nuclear bombs. American officials, however, have not been able to verify that. 

At a news conference today at his ranch with Italy's prime minister, Silvio Berlusconi, Mr. Bush also revived charges against Iran and Syria, warning that they would be "held accountable" if they continued to aid terrorists in the Middle East or disrupted the occupation of Iraq. 

He said both countries had harbored terrorists, and he called their behavior "unacceptable."

Administration officials said today that Mr. Bush's tough comments about Iran and Syria and his far more moderate tone about North Korea had been carefully calibrated. Even as they are focused on the Middle East peace effort, some administration officials have clearly concluded that North Korea may be on the verge of declaring itself a nuclear state, and that there is not much they can do to stop it.

"We're alert to the fact that this could be the summer surprise," a senior official said. "The president's words were intended to give diplomacy another chance."

Another senior Bush aide said on Sunday that the administration believed that it still had time to defuse the North Korean situation and that a confrontation might be exactly what North Korea was trying to provoke, to extract economic concessions from the West.

One result is a strategy that appears to be the opposite of the administration approach to Iraq: for each new North Korean declaration, Mr. Bush has responded with the equivalent of a shrug. Or, as Secretary of State Colin L. Powell once put it, the message to a starving North Korea will be, "You can't eat plutonium."

But privately, some administration officials worry that the strategy may not be sustainable if the North conducts a nuclear test to declare itself a nuclear power. 

The North has demanded both economic aid and a nonaggression pact, and the Bush administration has said it will not negotiate under conditions of blackmail. However, administration officials have said they will consider formalizing the verbal guarantees Mr. Bush has made that the United States will not attack the North without provocation.

Chinese officials are pushing the administration to hold talks with North Korea in August in Beijing. Mr. Bush has insisted that South Korea and Japan must be part of any talks. Today, he said he wanted those nations to speak "with a single voice that says to Mr. Kim Jong Il, `A decision to develop a nuclear arsenal is one that will alienate you from the rest of the world.' "

On the Middle East, White House officials have said Mr. Bush will meet on Friday with Mahmoud Abbas, the Palestinian prime minister, and presidential aides fear that whatever hopes they have placed in his authority are being undermined by elements seeking to prevent him from making concessions.

Once again today Mr. Bush praised Mr. Abbas, saying he and Prime Minister Ariel Sharon of Israel "are showing leadership and courage" even as their talks appear stalemated. He sent a message today that neighboring states must help or keep their hands off.

"Now it is time for governments across the Middle East to support the efforts of these two men by fighting terror in all its forms," he said. He added that "this includes the governments of Syria and Iran," which "continue to harbor and assist terrorists."

Mr. Bush last discussed Syrian and Iranian interference shortly after the end of the Iraq war, in April. He did not address that issue today, other than to say: "There are people in Iraq who hate the thought of freedom. There are Saddam apologists who want to try to stay in power through terrorist activity."

Mr. Berlusconi's invitation to talks here was largely a political reward for Italy's support for the Iraq war, and a not-so-subtle slap at France and Germany, whose leaders have been conspicuously left off the Crawford invitation list. 

Mr. Bush said he and Mr. Berlusconi had discussed how to entice other nations to help rebuild Iraq. There have been few volunteers to aid in peacekeeping, and many European nations believe the United States is reserving the most profitable reconstruction projects for Americans. Mr. Bush said reconstruction "shouldn't be viewed as a political exercise — it shouldn't be viewed as an international grab bag."