The United States on Tuesday dismissed Iranian threats to shut down the Strait of Hormuz as those of a weakened, isolated regime but said it was not seeking a "confrontation" with Tehran.
Tensions have soared over the vital oil route as Iran has threatened to choke off shipping or go after American naval ships if Western governments implement the latest round of punitive sanctions over its nuclear program.
Iran's military warned on Tuesday that it would not allow a US aircraft carrier to return through the Strait of Hormuz, but the Pentagon insisted it had no plans to pull warships out of the Gulf region.
"No one in this government seeks confrontation over the Strait of Hormuz. It's important to lower the temperature," Pentagon press secretary George Little told reporters, playing down fears of an escalation.
The White House and the State Department, however, still talked tough, saying that the Islamic republic's reaction showed that Western diplomatic pressure and sanctions were having an effect.
Iran's latest warning "reflects the fact that Iran is in a position of weakness," White House spokesman Jay Carney told reporters, adding that Tehran's threats suggest "a measure of the impact that the sanctions have been having on Iran."
Carney said Iran's leaders were under pressure because they had failed to meet their international obligations over the country's nuclear program, which the West charges is designed to produce atomic weapons.
"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," State Department spokeswoman Victoria Nuland said.
Iran's leaders "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.
Iran's military chief warned Tuesday that an American aircraft carrier, the USS John C. Stennis, should not return to the Gulf.
The Stennis passed through the Strait of Hormuz from the Gulf last week and is now in the Arabian Sea providing air support with its fighter jets to NATO-led forces in Afghanistan, according to the US Navy.
It was not clear when the carrier and accompanying warships would travel back through the strait, through which 20 percent of the world's oil flows.
After Tehran's threat to the aircraft carrier, the US military said it was committed to keeping warships in the region and that the movement of its naval vessels through the Strait of Hormuz was in compliance with maritime law.
"The deployment of US military assets in the Persian Gulf region will continue as it has for decades," Little said in a statement.