US officials in recent weeks had warned that they expected an uptick in attacks against US forces in Iraq and Syria, in part because of the second anniversary of the killing of top Iranian general Qassem Soleimani.
A similar attack was foiled on Monday, when Iraqi air defences downed two drones as they approached a base hosting US forces near Baghdad's international airport.
Separately, another coalition official told Reuters that the coalition had carried out strikes against an "imminent threat" after they saw several rocket launch sites near the Green Village in Syria.
While this official did not say which country in the coalition carried out the strikes or who was responsible for the launch sites, Iranian-backed militia forces have occasionally targeted US forces in both Iraq and Syria.
In Washington, the Pentagon said the coalition strikes in Syria were not carried out by aircraft, but did not provide more details on the threat.
"I'm not in a position now to get into specific attribution. That said, we continue to see threats against our forces in Iraq and Syria by militia groups that are backed by Iran," Pentagon spokesman John Kirby told reporters.
The United States is leading the international military coalition fighting Islamic State militants in Iraq and in Syria.
There are roughly 900 US troops in Syria and another 2500 in Iraq.
Soleimani was killed on January 3, 2020, in a drone strike near Baghdad airport ordered by then-US president Donald Trump.
Iranian President Ebrahim Raisi said on Monday that Trump must face trial for the killing or Tehran would take revenge.
