JERUSALEM (AP) — Defense Secretary Lloyd Austin said Thursday it's time to further disable Iran-backed militias that have struck at U.S. forces and ships in the Middle East and the U.S. is preparing to take significant action in response to the deaths of three U.S. service members in Jordan.

For days the U.S. has hinted strikes are imminent. While the threat of retaliation for Sunday's deaths has driven some militant groups to say they were stopping hostilities, as late as Thursday Yemen's Houthi rebels were still attacking vessels and fired a ballistic missile at a Liberian-flagged container ship in the Red Sea.

"At this point, it's time to take away even more capability than we've taken in the past," Austin said Thursday in his first press conference since he was hospitalized on Jan. 1 due to complications from prostate cancer treatment.

Previous U.S. strikes have not deterred the attacks. Since the war between Israel and Hamas broke out in October, Iranian-backed militant groups have struck U.S. bases in Iraq and Syria at least 166 times with rockets, missiles and one-way attack drones, drawing about a half-dozen U.S. counterstrikes on militant facilities in both countries. The U.S. military also has carried out airstrikes targeting the Iran-backed Houthi rebels in Yemen.

In the Red Sea, the Houthis have fired on commercial and military ships almost 40 times since November. In the latest attack, they fired a ballistic missile at a Liberian-flagged container ship on Thursday, U.S. defense officials said.

The attack happened west of Hodeida, a port city in Yemen long held by the rebels, said the United Kingdom Maritime Trade Operations, a British military group overseeing Mideast waterways. It said the crew and the vessel were safe and the blast came far off the vessel's starboard side.

The U.S. defense officials identified the targeted container ship as the Koi, a Bermuda-owned vessel. Its management could not be immediately reached for comment. The officials spoke on condition of anonymity to discuss intelligence matters. The Houthis did not claim responsibility for the assault.

The private security firm Ambrey reported Wednesday night that a ship was targeted with a missile southwest of Aden, Yemen, near the Bab el-Mandeb Strait between the Red Sea and the Gulf of Aden. The Houthis claimed that attack also targeted the Koi, though American officials had no immediate information on any attack Wednesday night.

The Houthis say they are targeting ships over Israel's offensive in Gaza against Hamas. But they have frequently targeted vessels with tenuous or no clear links to Israel, imperiling shipping in a key route for global trade between Asia, the Mideast and Europe.

The Houthis hit a commercial vessel with a missile on Jan. 26, sparking a fire that burned for hours.

Late Wednesday, American F/A-18 fighter jets struck and destroyed 10 Houthi drones that were prepared to launch, as well as a ground control station used by the rebels, the U.S. military said. The U.S. also intercepted a ballistic missile and other drones already in the air during the day.