Republican presidential hopeful Mitt Romney said Monday he would consider it an "act of war" if Iran was to shut down the Strait of Hormuz, a key transit route for global oil supplies.
"It is appropriate and essential for our military, for our navy to maintain open seas," Romney said at a debate between the four remaining Republican candidates in Tampa, Florida. "Of course it's an act of war."
Iran's military and political leaders have threatened to close the strait if increased Western sanctions over Tehran's suspect nuclear activities halt Iranian oil exports.
Iran's navy had specifically warned that it would react if the United States tried to redeploy one of its aircraft carriers to the waterway.
Hours before the debate the Pentagon confirmed that the US aircraft carrier USS Abraham Lincoln had passed through the Strait of Hormuz unaffected and was now in the Gulf.
Romney lamented what he described as weakened US military might, complaining "our navy is smaller than any time since 1917."
A former aide to President Barack Obama, David Axelrod, however quickly took to Twitter to rebut that point: "Note to Mitt," he wrote: "there are more active Naval ships today than there were when President Obama took office."
Romney, facing stiff opposition in the Florida primary race from rival Newt Gingrich, said the United States needed a US Navy so strong that enemies "couldn't possibly defeat us."
"We want to show Iran" that closing the Strait or any action similar act, Romney said, "will be considered an act of war, an act of terror and America is going to keep the sea lanes open."
On Friday, the New York Times, citing unnamed US officials, reported that the Obama administration had used a secret channel to warn Iran's supreme leader Ayatollah Ali Khamenei that closing the narrow strategic waterway would cross a "red line" and provoke a response.