The United States is building up its naval power in the Persian Gulf in response to threats by Iranian officials to close the Strait of Hormuz in case of further sanctions, the Los Angeles Times reported on Wednesday.

The report came after, earlier this month, U.S. defense officials told the New York Times that American forces have been quietly introduced into the Persian Gulf in an attempt to deter Iran from blocking the strategic waterway, and to increase strike capability in case the nuclear standoff with Iran escalates to a military confrontation.

According to the report, the deployments were meant to bolster the U.S. military presence in the region while reassuring Israel that the Iranian nuclear issue is being handled.

The New York Times report quoted an unnamed "senior Defense Department official" who said, "The message to Iran is, ‘Don’t even think about it.’ Don’t even think about sending your fast boats out to harass our vessels or commercial shipping. We’ll put them on the bottom of the gulf.”

On Wednesday, the L.A. Times said the U.S. Navy has been deploying dozens of unmanned underwater craft, recently purchased in order to seek and destroy underwater mines in the area ahead of a possible clash with Iran. These miniature submarines – SeaFoxes, each approximately 4 feet long and weighing less than 100 pounds, are equipped with a camera, homing sonar and an explosive charge, the LA Times wrote.

Iranian generals have warned that they could close the Strait of Hormuz, a vital international oil route in the Persian Gulf - thus blocking a considerable share of global oil exports - if oil sanctions were imposed.

Washington has said it would not tolerate any closure of the strait - the export route for one third of all seaborne traded oil. U.S. Defense Secretary Leon Panetta has said such a move would require a response.

In addition to the unmanned submarines the U.S. military has deployed four MH-53 Sea Dragon helicopters and four minesweeping ships in the region, the Times reported, in addition to two aircraft carriers and a squadron of F-22 fighters previously deployed to the region.