Obama vetoes bill allowing 9/11 victims to sue Saudi

President Barack Obama on Friday vetoed a bill allowing 9/11 families to sue Saudi Arabia, risking a fierce public backlash and rare congressional rebuke.

While expressing "deep sympathy" for the families of the victims, Obama said the law would be "detrimental to US national interests."

The White House tried and failed to have the legislation -- which was unanimously passed by Congress -- scrapped or substantially revised.

Terry Strada, whose husband Tom was killed in World Trade Center Tower One, told AFP the 9/11 "families are outraged and very disappointed" by Obama's decision.

She vowed that the group would now lobby "just as hard as we possibly can" to have Congress overturn the decision.

Republican presidential nominee Donald Trump described the decision as "shameful."

Obama now faces the very real prospect of Republican and Democratic lawmakers joining forces to override his veto for the first time in his presidency.

Such a rebuke -- which Congressional sources say could come as early as next Tuesday -- would mark Obama's last months in office and show the White House to be much weakened.

Families of 9/11 victims have campaigned for the law -- convinced that the Saudi government had a hand in the attacks that killed almost 3,000 people.

Fifteen of the 19 hijackers were Saudi citizens, but no link to the government has been proven. The Saudi government denies any links to the plotters.