Iran's stepped-up bellicosity, including a warning Tuesday that a U.S. aircraft carrier should not return to the Persian Gulf, is a reaction to increased talk in the United States and Israel of a strike on its nuclear sites, and of the West adding economic sanctions on its already struggling economy, analysts say.
The Pentagon responded to Iran's tough talk by vowing that its warships are in the Gulf to stay and will take steps to ensure the commercial oil shipping continues to sail through the Strait of Hormuz. More than one-sixth of the world's crude oil moves through the strategic sea lane at the mouth of the Gulf.
"This may very well be Iranian rhetoric, but we can't treat it as simple rhetoric," a senior U.S. official told The Washington Times.
"We have to take threats from the Iranians seriously, even if we don't think they'll necessarily follow through on them. The United States wouldn't tolerate the closure of the Strait of Hormuz."
Iran just completed a 10-day naval exercise that it said was designed to show it has the military capability to close Hormuz. Iran's army chief, Gen. Ataollah Salehi, upped the ante when he said the aircraft carrier USS John C. Stennis, which left the Gulf last week, must not return.
"I advise, recommend and warn [the U.S.] over the return of this carrier to the Persian Gulf, because we are not in the habit of warning more than once," the semi-official Fars news agency quoted Gen. Salehi as saying.
Aircraft carriers, studded with F-18 strike jets, typically move in and out of the Gulf during six-month deployments, spending some time in the Arabian Sea to support U.S. forces in the Afghanistan War.
Tehran is feeling pressure from Western sanctions as well as harsh rhetoric of American politicians in a presidential election year, including from candidates who vow to bomb the country's far-flung nuclear facilities to keep Iran from assembling atomic weapons.
Larry Johnson, a former CIA analyst, noted that congressional Republicans and Democrats approved sanctions on Iran that are even tougher than the Obama administration sought.
"If you are an Iranian intelligence analyst monitoring what the United States is saying, across the board there appears to be widespread support from the top of the political leadership on both sides for pursuing military action against Iran if there is a perceived movement toward developing nuclear weapons," Mr. Johnson said.
Iran's warning, he said, "accompanies the increased amount of rhetoric out of the United States, and they see the global effort to impose sanctions on them. I think it's a natural reaction."
Mr. Johnson said Iran would actively move to close the strait only in response to what it might see as an act of war by the West.
"Iran is not going to take any initiative unless they are backed into a corner," he said.
"And being backed into a corner means if oil sanctions are fully put in place. If they can really no longer export and collect revenues from their oil, then under those circumstances, yes, I can see making an effort to block the Strait of Hormuz."
He added that Iran would not be able to close the strait permanently.
"But I've heard some of our analysts say the 5th Fleet could open it in a heartbeat. Well, maybe yes, maybe no," he said.
The U.S. Navy's 5th Fleet is based in Bahrain and must sail through the Strait of Hormuz.
Added to the U.S. political rhetoric was the stark warning to Iran from Defense Secretary Leon E. Panetta.
"The United States does not want Iran to develop a nuclear weapon," Mr. Panetta said in a Dec. 19 interview with CBS News.
"That's a red line for us, and that's a red line, obviously, for the Israelis. If we have to do it, we will deal with it. ... If they proceed, and we get intelligence that they are proceeding with developing a nuclear weapon, then we will take whatever steps necessary to stop it."
Panetta spokesman George Little added Tuesday that the "deployment of U.S. military assets in the Persian Gulf region will continue as it has for decades."
U.S. aircraft carrier strike groups visit the Gulf on "regularly scheduled movements in accordance with our long-standing commitments to the security and stability of the region and in support of ongoing operation." Mr. Little added.
He said the deployments are to maintain support for the U.S. Central Command, which has responsibility for most of the Middle East and Central Asia.
"Our transits of the Strait of Hormuz continue to be in compliance with international law, which guarantees our vessels the right of transit passage," he said.
James Phillips, a Middle East analyst at the Heritage Foundation, said Iran's threats are intended to make Europe think twice about more moves against the hard-line Islamic state.
"I think the Iranians are playing up their threats to block the Strait of Hormuz in order to deter an Israeli or U.S. preventive attack on their nuclear program, dissuade the Europeans from imposing more sanctions and push up the price of oil, their foremost export, in nervous world oil markets," Mr. Phillips said.
But, he added, that in the end, shutting down shipping would come back to haunt Tehran.
"If the strait is closed, Iran actually would be one of the biggest losers," he said.
"Virtually all of its exports must be shipped through the strait, but Saudi Arabia, Iraq and Kuwait have access to pipelines through which they can export oil through the Red Sea or through Turkey to the Mediterranean Sea.
"Tehran would only try to close the strait as a last resort in the event that its own oil exports already were being embargoed or otherwise blocked."
State Department spokeswoman Victoria Nuland all but scoffed at Iran's threats and highlighted the fact that the value of Iran's currency is falling under the weight of sanctions.
"Frankly, we see these threats from Tehran as just increasing evidence that the international pressure is beginning to bite there and that they are feeling increasingly isolated and they are trying to divert the attention of their own public from the difficulties inside Iran, including the economic difficulties as a result of the sanctions," she said.
"I also ... take note of the fact that there seems to have been a significant drop in the Iranian currency, and that's, you know, among the measures of how these sanctions are biting on the country."
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