The latest in a series of Iranian threats to block the vital Strait of Hormuz triggered a sharp response Wednesday from the U.S. Navy, although there appeared to be little chance that Tehran would make good on its warnings.

Despite threats to close the narrow waterway if Western nations tighten sanctions on Iran by imposing an oil embargo, the Islamic republic needs the strait at least as much as its adversaries do, Iranian and foreign analysts said.

Iran, which feels threatened by the presence of U.S. bases and warships in the region, has warned for years that it would choke off the Strait of Hormuz in the case of war or economic sanctions. The passage at the entrance to the Persian Gulf hosts a daily caravan of tankers that transport roughly a third of the world’s oil shipments.

The European Union, encouraged by the United States, is expected to decide in January whether to boycott Iranian crude. And countries such as Japan and South Korea are under increasing U.S. pressure to stop buying oil from Iran, the world’s fifth-largest producer.

By undermining Iran’s ability to generate income through oil sales, the United States hopes to force Tehran to abandon its uranium enrichment program, which the Obama administration suspects is secretly aimed at enabling Iran to build nuclear weapons. Iran denies it is trying to build nuclear arms.

Iranian Vice President Mohammad Reza Rahimi, seen here in 2006, told students Tuesday that Iran would close the Strait of Hormuz in reprisal for any Western boycott of Iran’s oil. (AFP/Getty Images)

The latest furor erupted when Iranian Vice President Mohammad Reza Rahimi told students Tuesday that Iran would close the strait in reprisal for any Western sanctions on Iran’s oil exports.

In that case, “not even a drop of oil will flow through the Strait of Hormuz,” Rahimi said, according to the state-run Islamic Republic News Agency (IRNA). Iran’s navy commander, Rear Adm. Habibollah Sayyari, later said that for the nation’s armed forces, closing the strait would be “easier than drinking a glass of water.”

A closure could prompt a spike in oil prices, analysts said, further damaging the troubled world economy.

In addition to the threats, Iran has started a 10-day naval exercise to demonstrate what it calls “asymmetrical warfare,” a military doctrine aimed at defeating U.S. aircraft carriers in a potential Persian Gulf conflict by using swarms of rocket-mounted speedboats and a barrage of missiles.

“Does the West expect us to be threatened and attacked and we just surrender?” asked Ali Akbar Javanfekr, head of IRNA and an unofficial spokesman for President Mahmoud Ahmadinejad. “What are our options? Be sure, we can find ways to tackle any sanctions.”

In Bahrain, home of the U.S. Navy’s 5th Fleet, a spokeswoman for the fleet said no country would be allowed to block the strategically crucial strait. The Navy is “ready to counter malevolent actions,” Lt. Rebecca Rebarich added.

“Anyone who threatens to disrupt freedom of navigation in an international strait is clearly outside the community of nations,” Rebarich said in a statement. “Any disruption will not be tolerated.”

A State Department spokesman played down the latest warnings as “more rhetoric from the Iranians,” suggesting that the Obama administration did not perceive a serious threat to shipping in the Strait of Hormuz. “We’ve seen these kinds of comments before,” the spokesman, Mark Toner, said Wednesday.

“As the 5th Fleet has said, and I believe other governments have also said, it’s absolutely critical that there be freedom of navigation in these international waters,” Toner added.

Oil producers have not sat idle after decades of Iranian threats to shut off the only regional energy transportation corridor. The United Arab Emirates has nearly finished a 2.5 million-barrel-a-day pipeline circumventing the Persian Gulf. U.A.E. officials say the Abu Dhabi Crude Oil Pipeline Project is a “strategic pass,” circumventing the Hormuz Strait in case Iran closes the choke point.

Iranian officials insist that the U.A.E. pipeline and others that are being constructed in the region will not lessen the strategic importance of the Hormuz Strait. But they have raised the issue repeatedly, which analysts say is a sign that they are nervous about it.

And Iran — which has enjoyed record oil profits over the past five years but is faced with a dwindling number of oil customers — relies on the Hormuz Strait as the departure gate for its biggest client: China.

“We would be committing economical suicide by closing off the Hormuz Strait,” said an Iranian Oil Ministry official who spoke on the condition of anonymity because of the sensitivity of the subject. “Oil money is our only income, so we would be spectacularly shooting ourselves in the foot by doing that.”

Ahmad Bakhshayesh Ardestani, a political scientist running for parliament from the camp of hard-line clerics and commanders opposing Ahmadinejad, said it is “good politics” for Iran to respond to U.S. threats with threats of its own.

“But our threat will not be realized,” Ardestani said. “We are just responding to the U.S., nothing more.”

Staff writer Joby Warrick in Washington and special correspondent Ramtin Rastin in Tehran contributed to this report.