WASHINGTON — As Undersecretary of State Nicholas Burns prepares for a meeting with the five permanent members of the U.N. Security Council in Berlin tomorrow to discuss imposing tough sanctions on Iran, neither the Bush administration nor some of the most hawkish Republicans in Congress are yet willing to consider military force if those sanctions fail to halt Iran’s nuclear program.

The idea of putting a war resolution against the Islamic Republic to Congress was floated Monday on Fox News by the editor of the Weekly Standard, William Kristol. A resolution authorizing force against Iran for its defiance of a U.N. deadline to end uranium enrichment, as well as against Sudan for stepping up its military offensive in Darfur, would be a sufficiently “credible threat,” Mr. Kristol said. “And that would be something, if you did it in the next week or two, that could shake up the election,” he added.

Yesterday, however, the proposal received a lukewarm reaction at the White House and from two pro-Bush administration senators.

“As the president has emphasized throughout, we are seeking a diplomatic solution to the problem with the Iranian regime. The president could not have stated it more emphatically on numerous occasions,” a spokesman for the National Security Council, Frederick Jones, said.

Another administration official who requested anonymity called the idea “ludicrous” and added, “That’s not even a consideration.”

“The situation in Iran is not improving, and Senator Brownback prefers to leave all options on the table,” a spokesman for Senator Brownback, Brian Hart, said. A Republican of Kansas, Mr. Brownback won a battle in 2003 to raise small sums of public money to sponsor Iranian democracy activities in Iran.

Mr. Hart added that the senator “feels that at this time the best course of action in Iran is democratization efforts and regime change from within.”

An aide to Senator Santorum, a Republican of Pennsylvania who authored legislation that would authorize funding and support for internal opponents to the Iranian regime, pointed out that for now at least, her boss also favors internal regime change.

“As the senator noted on Sunday, the Senate needs to pass the Iran Freedom and Support Act, the bill that he introduced two years ago,” the aide said. “That bill gives the United States an opportunity to go after Iran by using pro-democracy forces within Iran and outside of Iran, and to do something to crack down on that regime with additional sanctions. So far the administration has opposed Senator Santorum on that effort.”

In June, the State Department helped thwart Mr. Santorum’s plan to attach the measure to an Iran resolution after Secretary of State Rice announced that America would be prepared to participate in talks with Iran on its nuclear program if it stopped enriching uranium.

Iran’s defiance of a Security Council deadline to end that enrichment presents President Bush with a dilemma.

While Mr. Bush has identified Iran as a charter member of the “axis of evil” and has said he will not tolerate an Iranian nuclear bomb, analysts have said any attack on Iran’s nuclear facilities could prompt a Shiite uprising in Iraq, where American military commanders have already accused the Iranians of supplying weapons to insurgents attacking coalition forces. The toppling of Saddam Hussein appears to have severely inhibited America’s ability to take military action against Iran.

Another risk in pressing Congress for a war resolution now is that it could fail to gain enough support.

“Right now the public is vacillating. Something like this, even if it becomes necessary, could well backfire,” a conservative foreign policy analyst who requested anonymity said yesterday. “What if the administration can’t make the case that Iran is really a menace and the resolution goes down because the CIA sabotages them again?”

The deputy director of the Washington Institute for Near East Policy, Patrick Clawson, said: “The U.S. government is pursuing multilateral diplomacy with the Europeans in the lead, and the Bush administration is pleased that this is an issue where they can present themselves as multilateral to the core. If the United States or Congress were to discuss such a resolution, the rumor mill in the Middle East would go into overtime, saying the United States will actually do this.”

The sanctions diplomacy currently under consideration includes U.N.-led measures as well as a voluntary plan agreed on by Europe, Japan, and America to deny Iranian banks access to American dollars. For the last year, the Treasury Department has pressed European banks to begin divesting from Iran, pointing out that banks that do business with Iran might have their access to American financial markets restricted.

“Any discussion about the need for military action against Iran highlights the problem with the diplomatic process,” the vice president for foreign and defense policy studies at the American Enterprise Institute, Danielle Pletka, said. “It has become clear that effective multilateral action is all but impossible. That leaves the United States in the position of choosing between doing nothing and military conflict with Iran.”