Secretary of State Hillary Clinton warned Iran Wednesday that the United States would extend a "defense umbrella" over its allies in the Persian Gulf if the Islamic Republic obtains a nuclear weapons capability.

Appearing on a Thai TV program, Clinton said the U.S. would also take steps to "upgrade the defense" of America's Gulf allies in such an event, a reference to stepped-up military aid to those countries.

Clinton's reference to a U.S. "defense umbrella" over the Persian Gulf represented a potentially significant evolution in America's global defense posture. Washington already explicitly maintains a "nuclear umbrella" over Asian allies like Japan and South Korea, but seldom, if ever, has any senior U.S. official publicly discussed the concept in relation to the Gulf.

The secretary's remarks also suggested the course the Obama administration might pursue if, as many analysts predict, an unchecked Iran succeeds in obtaining a nuclear weapons capability before President Obama's term expires -- in effect, how the United States might live with a nuclear-armed Iran. Clinton's comments evoked a vision of the U.S. countering such a threat by bolstering regional defenses and reminding Iran of the dangers of mutually assured destruction -- but not by seeking regime change in Iran or by taking military action to destroy the country's nuclear apparatus.

"We want Iran to calculate what I think is a fair assessment that if the United States extends a defense umbrella over the region, if we do even more to support the military capacity of those in the Gulf, it's unlikely that Iran will be any stronger or safer because they won't be able to intimidate and dominate as they apparently believe they can once they have a nuclear weapon," Clinton said.

A senior aide to Clinton, speaking to reporters on background while the secretary's traveling party flew from Bangkok to Phuket, said Clinton's comments did not reflect her acceptance of a nuclear-armed Iran nor a literal accounting of what the U.S. would do if Tehran did acquire nuclear weapons. 

Rather, the aide said, the secretary was only articulating what arguments the Obama administration makes to influence Iran's calculus. The aide also said Clinton's use of the term "defense umbrella" was not synonymous with the term "nuclear umbrella," even though the context of her comments centered on Iran's potential acquisition of nuclear weapons.

In Jerusalem, though, Dan Meridor, Israel's Minister of Intelligence and Atomic Energy, told Army Radio: "I was not thrilled to hear the American statement from yesterday that they will protect their allies with a nuclear umbrella, as if they have already come to terms with a nuclear Iran. I think that's a mistake."

Asked about the Obama administration's attempts to engage Iran, Clinton said she "had hoped we would get a positive response ... but then their elections happened." Clinton told her Thai TV interviewers there was "no doubt" that "irregularities" occurred in Iran's disputed presidential election and that the regime then "brutally repressed" those citizens that protested the announced outcome.

Because of these events, the secretary said, the Iranian regime has been "preoccupied" and thus not responded to American overtures. "The nuclear clock is ticking," she said, noting that Tehran has continued to pursue its nuclear programs and adding that the U.S. and its allies in the nuclear diplomacy surrounding Iran "will not keep the window open forever." She repeated previous pledges to work to impose "crippling" sanctions if Iran does not halt its enrichment of uranium.

The Associated Press contributed to this report.