President Joe Biden said on Friday the United States is not seeking conflict with Tehran, after Washington carried out strikes on Iran-linked groups in Syria in retaliation for a deadly drone attack.
A war monitor said 14 people were killed in the strikes. They came after the Pentagon said a US contractor died, and another contractor and five military personnel were wounded by a kamikaze drone "of Iranian origin" that struck a US-led coalition base near Hasakah in northeastern Syria.
In response, US Defence Secretary Lloyd Austin said on Thursday that, at Biden's direction, he had ordered the "precision air strikes tonight in eastern Syria against facilities used by groups affiliated with Iran's Islamic Revolutionary Guard Corps".
But the US president sought to lower the temperature on Friday, saying the United States "does not seek conflict with Iran, but is prepared to act forcefully to protect our people".
Hours after the strikes, the US Central Command (CENTCOM) said 10 rockets were fired at American and coalition forces at the Green Village base in northeast Syria.
There were no injuries or damages to facilities at the base, but one rocket struck a home around three miles (five kilometres) away, causing minor wounds to two women and two children, CENTCOM said.
The Syrian Observatory for Human Rights, a Britain-based monitor with a wide network of sources on the ground, said 14 people had been killed by the US strikes in Syria, and later reported a fresh rocket fire and more strikes in response.
Militias affiliated with Iran's Revolutionary Guard have a heavy presence across Syria, especially around the border with Iraq, and south and west of the Euphrates in Deir Ezzor province, where the latest US strikes took place.
The United States has about 900 troops in posts across northeastern Syria to keep pressure on the remnants of the Islamic State group and support the Kurdish-led Syrian Democratic Forces, which control most of the northeast.
The Pentagon said two F-15 fighters launched the retaliatory attack – which spokesman Pat Ryder said was to protect US personnel – in the early morning hours local time.
"The strikes that we took last night were intended to send a very clear message that we will take the protection of our personnel seriously and that we will respond quickly and decisively if they are threatened," he said.
They were "proportionate and deliberate action intended to limit the risk of escalation to minimise casualties," he said.
US personnel in Syria have frequently been targeted in attacks by militia groups the United States says are backed by Tehran.
Two of the US service members wounded on Thursday were treated on site, while the three other troops and one US contractor were evacuated to Iraq, the Pentagon said.
"We will always take all necessary measures to defend our people and will always respond at a time and place of our choosing," said CENTCOM chief General Michael Kurilla.
In January, the US military said three one-way attack drones were launched against the Al-Tanf garrison in Syria, with one breaching its air defences and wounding two allied Syrian fighters.
Last August, Biden ordered similar retaliatory strikes in Deir Ezzor province after several drones targeted a coalition outpost, without causing any casualties.
"We know that these groups are sponsored by Iran," Ryder said.
"So Iran certainly plays a role in terms of ensuring that this type of activity doesn't happen," he said.