U.S. forces hit three Iranian oil tankers after Navy warships came under missile attack, the American military said Saturday.

It warned it would "if necessary, destroy Iran's limited and exposed oil fleet."

Experts called the move a dangerous step up after Iran's earlier attacks at sea had targeted commercial ships.

The strikes came a day after President Donald Trump called the conflict "small potatoes."

They mark a return to fighting after six months of on-and-off war that began with U.S. and Israeli attacks on Iran on Feb. 28.

The military said an American aircraft carrier and a destroyer avoided "multiple unprovoked Iranian attacks," and no U.S. personnel were hurt.

Two Iranian oil carriers were "permanently disabled," and a third, empty one, was destroyed.

Iran's joint military command warned that strikes against U.S. military ships would be worse if the U.S. keeps blocking Iranian shipping, state media reported.

Danny Citrinowicz, an Iran expert at Israel's Institute for National Security Studies, said the missile attack on a U.S. carrier showed Tehran was taking risks it had avoided before.

The U.S. said one tanker was hit near Kharg Island, another near Jask, and the empty one in the Gulf of Oman, where its crew was told to leave the ship.

The latest strikes came almost a week after the U.S. and Iran restarted attacks following a month of calm.

At least five people were killed earlier in the week during a U.S. bombing of southern Iran, including one strike that hit a wedding.

Two teenage girls hurt in that attack described explosions and injuries in hospital interviews.

The Trump administration has mixed military actions with pressure on foreign banks that handle Iran's money, while Vice President JD Vance said talks were unlikely while Iran targets ships.