Iran's threats to seal off the Strait of Hormuz to international oil shipments are the latest in a series of escalating moves by the regime in response to impending Western sanctions, experts said.
Iran's navy chief, Adm. Habibollah Sayyari, told state-run TV Wednesday that closing the Persian Gulf choke point "is very easy for Iranian naval forces."
It was the second such threat in as many days after Vice President Mohamed Reza Rahimi vowed on Tuesday to close the strait, cutting off oil exports, if the West imposes sanctions on Iran's oil shipments.
In response, a spokeswoman for the U.S. 5th Fleet warned that any disruption at the strait "will not be tolerated." Lt. Rebecca Rebarich said the U.S. Navy is "always ready to counter malevolent actions to ensure freedom of navigation."
Raymond Tanter of the Iran Policy Committee said the escalating rhetoric could have consequences.
"I think that now that the threat is in place, the regime in Tehran is going to be hard-pressed not to try to carry it out," Tanter told NPR.
Tanter said the move is the latest to ratchet up tensions between Iran and Western nations. The Iranian regime is thought to be behind a plot to assassinate the Saudi ambassador to Washington, a mob attack on the British embassy in Tehran and rocket attacks on Iranian opposition groups in Iraq.
The U.S. and its allies have accused Iran of using its civilian nuclear program as a cover to develop nuclear weapons. Tehran has denied the charges, saying its program is geared toward generating electricity and producing medical radioisotopes to treat cancer patients.
Military Muscle Flexing
Iran has adopted an aggressive military posture in recent months in response to increasing threats from the U.S. and Israel that they may take military action to stop Iran's nuclear program.
Iran's naval forces are in the midst of a 10-day exercise near the Strait, and the regime has stepped up its rhetoric in recent days as President Obama prepares to sign legislation to implement anti-nuclear sanctions that target the country's oil revenue.
Closing off the waterway that serves as a conduit for up to 20 percent of the world's oil shipments is "something that they absolutely could do if they wanted to," said Christopher Steinitz, a research analyst at CNA Strategic Studies.
"I think there are those [in the Iranian government] who are willing to do so, especially if they see the situation economically as leaving them no alternative," Steinitz said, adding that "we know they are very worried about the impending sanctions."
The most likely move by Iran would be to turn the narrow maritime passage into an underwater minefield, just as Tehran did in 1987, Steinitz said.
"As we saw then, it's a phenomenon that really does get the world's attention and sort of rallies an international response," he said.
Oil Markets Stay Calm
Saudi Arabia's reassurance that it could make up for lost oil supplies if Iran should make good on the threat helped calm world oil markets on Wednesday.
World oil prices actually dropped a bit. In New York, benchmark crude fell 77 cents to $100.57 a barrel in morning trading. Brent crude fell 82 cents to $108.45 a barrel in London.
Iran is the world's fourth-largest oil producer, with an output of about 4 million barrels of oil a day. It relies on oil exports for about 80 percent of its public revenues.
The country's navy has become increasingly sophisticated in recent years, acquiring a number of fast-moving surface vessels, Soviet Kilo-class submarines, and upgrading its missile capabilities. It claims to have sonar-evading submarines designed for shallow waters of the Persian Gulf.
Iranian media have described how its navy could use a combination of warships, submarines, speedboats, anti-ship cruise missiles, torpedoes, surface-to-sea missiles and drones to stop ships from sailing through the Strait.
Iran claimed a victory this month when it captured an American surveillance drone almost intact. It went public with its possession of the RQ-170 Sentinel to trumpet the downing as a feat of Iran's military in a complicated technological and intelligence battle with the U.S.
American officials have said that U.S. intelligence assessments indicate the drone malfunctioned.
NPR's Scott Neuman contributed to this report, which includes material from The Associated Press.