The US military has struck Iran-backed militias in eastern Syria, killing at least 22 fighters according to a war monitor, in what the Pentagon said was a message from the new administration after recent rocket attacks targeting US troops in Iraq.
In its first military action against Iran-linked groups since Joe Biden became president five weeks ago, the Pentagon said it had carried out air strikes on Thursday at a Syria-Iraq border control point used by Iran-backed groups, destroying "multiple facilities".
"At President Biden's direction", the US raids targeted "infrastructure utilised by Iranian-backed militant groups in eastern Syria", spokesman John Kirby said in a statement.
"These strikes were authorised in response to recent attacks against American and coalition personnel in Iraq, and to ongoing threats to those personnel," he said.
The Syrian Observatory for Human Rights said all the dead were from Iraq's state-sponsored Hashed al-Shaabi paramilitary force, an umbrella group that includes many small militias with ties to Iran.
The attacks in Iraq laid down a challenge to the new Biden administration just as it opened a door to resumed negotiations with Tehran over its nuclear programme. But the administration has also made clear it will not brook "malign activities" in the region by Iran.
Meanwhile, Biden spoke with Saudi Arabia's King Salman bin Abdulaziz Al Saud on Thursday as the US prepares to release a report about the 2018 murder of Saudi journalist Jamal Khashoggi.
He "affirmed the importance the United States places on universal human rights and the rule of law", the White House said in a brief statement after the call.
Biden also emphasised the US commitment to assuring Saudi Arabia security from threats from Iran and discussed renewed diplomatic efforts to end the war in Yemen, the White House said.
The new Biden administration has taken a tougher stance towards Riyadh than the prior Trump administration, pushing for an end to the civil war in Yemen and greater recognition of human rights in the kingdom.