A US ship on Tuesday rescued six Iranian mariners in the Gulf after their boat broke down, the Pentagon said, in the latest such gesture despite soaring tensions between Washington and Tehran.

The United States, while pressing Iran over its nuclear program, has drawn attention to its assistance to ordinary Iranians twice in less than a week as US ships defy warnings from the Islamic regime not to enter strategic waters.

US officials said an Iranian crew used flares to seek help from the passing US ship after flooding in the engine room left their dhow unseaworthy before sunrise some 50 nautical miles (90 kilometers) southeast of the Iraqi port of Umm Qasr.

The Coast Guard cutter, the Monomoy, gave the Iranians water, blankets and meals made in accordance with Islamic law and provided medical care for one of the mariners who had suffered non-serious injuries, officials said.

A US military statement said that Hakim Hamid-Awi, the owner of the Iranian dhow named the Ya-Hassan, was thankful.

"Without your help, we were dead. Thank you for all that you did for us," the US statement quoted him as saying.

In the afternoon, US forces transferred the six mariners on inflatable boats to an Iranian Coast Guard vessel, the Naji 7, the statement said.

The captain of the Naji 7 also offered his regards to his US counterparts and "thanks us for our cooperation," according to the US statement.

The United States says that its forces routinely rescue sailors in distress regardless of nationality but officials have been eager to highlight efforts to assist Iranians amid the tensions at sea.

Last week, the US Navy rescued 13 Iranians held by pirates who were believed to come from Somalia. The operation was carried out by a warship escorting the USS John C. Stennis carrier, which Iran had warned not to return to the Gulf.

In rare praise for the United States, Iran welcomed last week's "humanitarian and positive act" but said it did not justify Western forces' deployment in the Gulf.

Iran has threatened to close off the Strait of Hormuz if the European Union moves ahead with a total ban on oil exports from Tehran.

The United States, which has had poor relations with Iran since the 1979 Islamic revolution, recently imposed tough sanctions aimed at foreign firms that buy from Iran.

Iran's threats have spooked oil markets as the strait is the sole waterway to the Gulf, the world's largest source of fossil fuels. But many analysts doubt that Iran has the military capability to block the strait.

Admiral Jonathan Greenert, the chief of US naval operations, said that he was focused on providing self-protection for forces in the Gulf.

"If you ask me what keeps me awake at night, it's the Strait of Hormuz and the business going on in the Arabian Gulf," he said, referring to the body which Iranians call the Persian Gulf.

"I want to make sure our folks have the right equipment to do the right thing," he said at the Center for a New American Security, a Washington think-tank.

Western powers fear that Iran, an arch-enemy of the West and Israel, is developing nuclear weapons. Iran insists that its program is solely for peaceful purposes.

Tensions have kept spiraling after Iran started enriching uranium in a new underground bunker and the Islamic regime sentenced to death an American ex-Marine of Iranian descent accused of spying.