The White House has warned of a possible military response to a rocket attack that hit an air base in western Iraq where American and coalition troops are housed.
A US contractor died after at least 10 rockets slammed into the facility early on Wednesday.
No one claimed responsibility for the attack, the first since the US struck Iran-aligned militia targets along the Iraq-Syria border last week.
"We are following that through right now," President Joe Biden told reporters on Wednesday.
"Thank God, no one was killed by the rocket but one individual, a contractor, died of a heart attack. But we're identifying who's responsible and we'll make judgments" about a response."
White House press secretary Jen Psaki suggested last week's "calculated" US airstrikes could be a model for a military response.
Those were in response to an attack on American forces in northern Iraq earlier in February.
"If we assess further response is warranted, we will take action again in a manner and time of our choosing," Psaki said.
Pentagon spokesperson John Kirby said the US contractor "suffered a cardiac episode while sheltering" from the attack and died shortly after.
He said there were no service members injured and all are accounted for. British and Danish troops also are stationed at the base.
The US airstrikes last week, which killed one member of the Iran-aligned militia, had stoked fears of another cycle of tit-for-tat attacks as happened more than a year ago.
Those included the US drone strike in January 2020 that killed Iranian General Qassim Soleimani in Baghdad and set off months of increased troops levels.
Wednesday's death heightens worries the US could be drawn into another period of escalating attacks, complicating the Biden administration's desire to open talks with Iran over the 2015 nuclear deal.
The latest attack also comes two days before Pope Francis is scheduled to visit Iraq despite concerns about security and the coronavirus pandemic.
The much-anticipated trip will include stops in Baghdad, southern Iraq and the northern city of Irbil.
The rockets struck Ain al-Asad airbase in Anbar province early in the morning, US-led coalition spokesperson Colonel Wayne Marotto said.
Kirby said the rockets were fired from east of the base and that counter-rocket defensive systems were used to defend forces at the base.
Kirby said the US can't attribute responsibility for the attack yet and that the extent of the damage was still being assessed.
Australian Associated Press