US not ruling out retaliation against Iran-backed groups after attacks on soldiers

The U.S. retains the ability to defend itself and hasn't ruled out retaliatory operations after the Pentagon said American forces were attacked by Iran-backed militants at least 13 times in the Middle East in the last week, President Joe Biden said Wednesday.

"My warning to the ayatollah [is] that if they continue to move against those troops, we will respond, and he should be prepared," Biden told reporters, referring to Iran's supreme leader.

Pentagon officials have echoed that.

"We will always maintain the inherent right of self-defense. And if there is a response, should we choose to have one, we would do that at a time and place of our choosing," Brig. Gen. Pat Ryder told reporters on Tuesday.

"We are preparing for this escalation both in terms of defending our forces and responding decisively," he said.

There is precedent for a potential military response: In recent years the U.S. has conducted retaliatory airstrikes targeting Iran-backed groups in Iraq following previous attacks on U.S. military bases.

Tensions have been rising in the Middle East in the wake of a Hamas terror attack on Israel on Oct. 7 which killed more than 1,400 people, according to Israeli officials.

Israel subsequently launched a war on Hamas in Gaza, the neighboring Palestinian territory controlled by the extremist group. More than 6,500 people have since been killed in Gaza, according to the Gaza Health Ministry that is run by Hamas. ABC News has not independently confirmed this casualty figure.

Leaders from Hamas, Palestinian Islamic Jihad, another Palestinian militant group, and the Lebanese militant group Hezbollah -- all of whom, the U.S. says, are sponsored by Iran -- reportedly met in Beirut on Wednesday.

Amid the unfolding conflict, the U.S. has surged military assets to the Middle East both in support of Israel's response to Hamas and as a deterrent to other countries, like Iran and their proxies, becoming involved, Defense Secretary Lloyd Austin said on Sunday on ABC's "This Week."

"We're concerned about potential escalation. In fact, what we're seeing is the prospect of a significant escalation of attacks on our troops and our people throughout the region," Austin told "This Week" co-anchor Jonathan Karl.

One of the American warships, the USS Carney, last week shot down multiple missiles and drones as they crossed the Red Sea after being launched by Iran-backed Houthis from Yemen, the Pentagon has said.

Ryder said on Wednesday that the missiles had the capability of reaching Israel, though the U.S. hasn't concluded who the target was.

Two U.S. officials told ABC News around 20 service members have sustained minor injuries, such as cuts and tinnitus, in the 13 attacks by the Iran-sponsored militias in Iraq and Syria since Oct. 17.

The attacks have included one-way drone assaults and rocket launches, according to the Pentagon. In the U.S. view, Iran bears responsibility because they have funded and supplied these militias, Ryder said Tuesday.

Ahead of any potential retaliatory moves, the U.S. has also sought to tamp down fears that the Israel-Hamas war could spiral out in the Middle East -- in the kind of escalation not seen there in decades.

"The United States does not seek conflict with Iran. We do not want this war to widen," Secretary of State Antony Blinken said at a meeting of the U.N. Security Council on Tuesday. "But if Iran or its proxies attack U.S. personnel anywhere, make no mistake: We will defend our people, we will defend our security -- swiftly and decisively."

ABC News' Matt Seyler contributed to this report.