US troops stationed in Iraq's Kurdistan Region were attacked on Thursday but the assault was unsuccessful, the Pentagon said.
“We are aware of an attack today against US forces at Erbil airbase in Iraq that was unsuccessful. No casualties, some minor damage to infrastructure,” Pentagon press secretary Brig Gen Pat Ryder told reporters.
The Pentagon reported that at least 21 US troops had experienced “minor injuries” from rocket and drone attacks in Iraq and Syria since October 17.
Brig Gen Ryder declined to say which specific group might have been behind the attacks, but "we know that these groups are affiliated with Iran".
He said about 900 more US troops are heading to the Middle East or have just arrived there to bolster air defences to protect American personnel amid the surge in attacks in the region.
He said two new Iron Dome missile systems in the US would be shipped to Israel as its war against Hamas in the Gaza Strip continues.
Iranian Foreign Minister Hossein Amirabdollahian told the UN on Thursday that if Israel's retaliation against Hamas in the Gaza Strip does not end, the US will "not be spared".
Last week off the coast of Yemen, a US warship shot down more than a dozen drones and four cruise missiles fired by Iranian-backed Houthis.
An Iranian proxy group in Iraq on Tuesday said it would expand attacks on US bases in the region.
US President Joe Biden on Wednesday issued a warning to Iran's supreme leader Ayatollah Ali Khamenei after the threats.
“My warning to the Ayatollah was that if they continue to move against those troops, we will respond,” Mr Biden said.
Brig Gen Ryder said any response would come “at a time and place of our choosing”.