BEIRUT (AP) — A U.S. airstrike targeting facilities used by Iran-backed militias in Syria appears to be a message to Tehran delivered by a new American administration still figuring out its approach to the Middle East.

The strike was seemingly a response to stepped-up rocket attacks by such militias that have targeted U.S. interests in Iraq, where the armed groups are based. It comes even as Washington and Tehran consider a return to the 2015 accord meant to rein in Iran’s nuclear program.

The U.S. appears to have chosen the target, just across the border in Syria rather than in Iraq, carefully. It's a way for President Joe Biden to signal he will be tough on Iran while avoiding a response that could offset the delicate balance in Iraq itself or trigger a wider confrontation.

And it's yet another example of how Syria, mired in civil war for the past decade, has often served as a proxy battlefield for world powers.

WHO ARE THE FORCES TARGETED BY THE US?

The U.S. airstrike — which took place Friday in Syria — targeted one of the most powerful Iran-backed militias in the Middle East known as Kataeb Hezbollah, or the Hezbollah Brigades. The group is part of the Popular Mobilization Forces, which includes an array of Iraqi militias.

The group was founded after the U.S.-led invasion of Iraq in 2003 that toppled dictator Saddam Hussein. It is different from Lebanon’s Hezbollah, but the two groups are strong allies. In recent years, Kataeb Hezbollah has played a major role in the fight against the Islamic State group as well as helping President Bashar Assad’s forces in Syria’s conflict.

The group was founded by Abu Mahdi al-Muhandis, a veteran Iraqi militant who was closely allied with Iran and killed in a U.S. drone attack in Baghdad in January 2020 along with Gen. Qassem Soleimani, the commander of Iran’s elite Quds Force.

The U.S. has hit the group before: In December 2019, an American strike along the Syria-Iraq border killed 25 of its fighters and wounded dozens. Washington called it retaliation for the death of an American contractor in a rocket attack that it blamed on Kataeb Hezbollah.

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WHAT DOES THIS MEAN FOR RELATIONS WITH IRAN?

The attack is likely aimed at sending a message to Tehran that the U.S. will not tolerate attacks against American interests in the region, while leaving the door open for talks.

It comes as the Biden administration faces an uncertain road in its attempts to resurrect the 2015 Iran nuclear deal — which gave Tehran billions of dollars in sanctions relief in exchange for curbs on its nuclear program and that the Trump administration pulled out of.

In the meantime, relations with Iran have been further strained as the country's proxies become more assertive, with Iran-backed militias increasingly targeting U.S. interests and allies. That has rekindled worries that the standoff relations between the U.S. and Iran could end up being fought out in Iraq.

Already there are signs that Iraq is being used to fight a proxy war. Explosive-laden drones that targeted Saudi Arabia’s royal palace in the kingdom’s capital last month were launched from inside Iraq, a senior Iran-backed militia official in Baghdad and a U.S. official told The Associated Press this week.

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WILL THIS TRIGGER A WIDER ESCALATION?

That is unlikely at this point.

Biden’s decision to attack in Syria does not appear to signal an intention to widen U.S. military involvement in the region, but rather to demonstrate a will to defend U.S. troops in Iraq while also avoiding embarrassing the Iraqi government, a U.S. ally, by striking on its territory.

Pentagon Spokesman John Kirby said the operation in Boukamal, Syria, sends an unambiguous message: “President Biden will act to protect American and coalition personnel. At the same time, we have acted in a deliberate manner that aims to deescalate the overall situation in eastern Syria and Iraq.”

A Syrian commentator based in Turkey, Abdulkader Dwehe, said the choice of Syria was a wise one.

“Responding in Iraq could open a front that may be hard to close,” he tweeted following the attack. “With the Boukamal strike, a valuable point, and a political message rather than a military one, have been made.”

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FOLLOWING IN THE FOOTSTEPS OF OTHER US PRESIDENTS

In its first weeks, the new Biden administration has emphasized its intent to put its focus on the challenges posed by China — even as volatility and threats to U.S. interests persist in the Middle East.

But the operation proved the region is never far from a U.S. president’s agenda.

By striking Syria, Biden joins every American president from Ronald Reagan onward who has ordered a bombardment of countries in the Middle East.