U.S. newspaper reports ("Washington Post"/"New York Times") cited Rice overnight as saying Washington would continue to stay out of a diplomatic initiative by France, Germany and Britain to persuade Iran to give up any ambition to develop nuclear weapons.
Her comments came after Bush, in his State of the Union speech on 2 February, expressed U.S. support for the European effort.
Amid intensifying U.S. rhetoric on Iran, analysts are struggling to decipher Washington's ultimate intentions.
Bush recently refused to rule out the use of force to neutralize suspected Iranian sites for developing atomic arms. Iran denies it is pursuing such arms.
Today, after meeting with British Prime Minister Tony Blair, Rice said the U.S. is n-o-t considering a military attack at this point.
"The question is simply not on the agenda at this point in time," she said. "You know, we have diplomatic means to do this. Iran is not immune to the changes that are going on in this region."
Analysts say emerging U.S. policy toward Iran remains hazy. But they agree there are senior officials in Washington who are seriously considering strategic strikes on suspected Iranian nuclear sites.
"There're a lot of people at very high levels in the administration, as of course you know, who take the surgical strike idea as really the only possible option," says Turi Munthe of London's Royal United Services Institute. "My understanding is that Rice is not part of that team, and Bush has been quite careful."
Munthe believes Washington is still far from making a decision on any strikes. He says the European initiative is still in midcourse and that there is still time, as most experts don't expect Iran to be able to build a nuclear weapon for at least another three years.
"I have the sense that if the 'EU-3' (France, Germany, Britain) is genuinely able to get some hard concessions from Iran, then [British Foreign Minister Jack] Straw, certainly, believes that he'll be able to get the Americans to play ball," Munthe says.
Presumably, for Washington, "playing ball" would mean refraining from military action and allowing diplomacy to run its course.
But others note there appears to be more to Washington's new rhetoric than stopping any perceived Iranian weapons program.
In his State of the Union speech, Bush put the spread of democracy and freedom in the Muslim world at the top of America's foreign policy agenda. And Bush made it clear that Iran looms large on that agenda: "To the Iranian people, I say tonight: As you stand for your own liberty, America stands with you."
Rice emphasized that message in her overnight remarks. Speaking on her plane, she criticized Iran's human rights record and said its religious leaders are bad for Iranians and the region.
Iranian-born Sharam Chubin is director of research at the Geneva Center for Security Policy in Switzerland. He tells RFE/RL that he believes Washington's ambitions in Iran extend beyond stopping any nascent atomic arms program.
"There's no question, in the closing months of the last year, after the election, and in the early part of this year, that's very much the focus," Chubin says. "Regime change seems to be policy -- again. The only problem with it is -- I say again because this is something that was highlighted a couple of years ago -- the problem with it is, it isn't really likely in Iran."
Chubin says Iran is probably the most mature regional candidate for democracy. But he says the opposition, as well as student activists, are now in retreat and that, while the majority of the population dislikes the regime, the citizenry is politically apathetic.
He believes excessive threats on Iran are likely to backfire.
"External threats only strengthen the regime because they can appeal to a sort of latent nationalism," Chubin says. "So you have the situation whereby appealing to Iranians' democratic instincts and by showing solidarity with the so-called reformists, what you are actually doing is quite often not only undermining them, but strengthening the regime. They turn around and say, 'Every time we want to act independently, they threaten us abroad. Every time we want to develop the full [nuclear] fuel cycle, we're put under sanctions.' You see, they play these games."
Iran, as well as the Middle East conflict and Iraq, are likely to be on Rice's agenda over the next week.
After London, she has planned stops in Germany, Turkey, Poland, Italy, France, Luxembourg, and Brussels, as well as Israel and the West Bank.