The U.S. military said Monday it destroyed six Iranian small boats and intercepted Iranian cruise missiles and drones as Tehran tried to disrupt President Donald Trump's new effort to reopen commercial shipping through the Strait of Hormuz.

US Says Iran Opened Fire First

Adm. Brad Cooper, head of Central Command, told reporters that Iran opened fire on U.S. warships in the Middle East and that American forces retaliated, destroying six Iranian small boats. Reuters reported that the clash came as Washington launched "Project Freedom," Trump's operation to restore commercial transit through one of the world's most important energy routes.

Cooper said he "strongly advised" Iranian forces to stay away from U.S. military assets as the Pentagon proceeds with the operation. He said the U.S. naval blockade, which bars vessels leaving Iranian ports from departing the region, remains in effect.

Project Freedom Clears Path Through Mines

Multiple U.S. Navy destroyers are positioned in the Persian Gulf, Cooper said. He added that U.S. forces have cleared an "effective pathway" through Iranian mines for commercial ships trying to cross the Strait of Hormuz.

Cooper said vessels from 87 countries are in the Persian Gulf and that the U.S. military has contacted dozens of ships and shipping companies over the past 12 hours to "encourage traffic flow" through the strait.

Two cargo ships passed through the waterway Monday under the protection of U.S. Navy guided-missile destroyers. An explosion hit a South Korean-operated ship in the strait, though Trump said on social media that the vessel was not part of the operation and suggested it should join U.S.-protected movements. Trump estimated the U.S. had sunk seven Iranian fast boats.

Iran Denies Claims As Trump Warns Tehran

Iran disputed the U.S. account. The Revolutionary Guards said no commercial vessels had crossed the strait in recent hours and called U.S. claims false, while Iranian state media denied that American forces had sunk Iranian vessels.

Meanwhile, Trump told Fox News on Monday that if Iran attacks American vessels, they will be "blown off the face of the Earth." Asked on "The Hugh Hewitt Show" whether the ceasefire was over or a U.S. attack was imminent, Trump replied, "Well, I can't tell you that."

The Iranian threat has left many ships stuck in the Gulf. Reuters notes that 805 commercial vessels, including tankers, container ships, auto carriers and bulk ships, transmitted automatic identification signals from inside the Gulf in the past 24 hours, citing MarineTraffic data.