WASHINGTON - President Barack Obama has vetoed a bill that would have allowed the families of 9/11 victims to sue the government of Saudi Arabia.

The move sets Obama up for a possible first veto override by Congress. Both chambers passed the bill by voice vote. The House sent Obama the bill just before the 15th anniversary of the attacks that killed nearly 3,000 people in New York, Washington and Pennsylvania on Sept. 11, 2001.

Obama says the bill would "upset longstanding international principles regarding sovereign immunity."

The bill would have given 9/11 families the right to sue in U.S. court for any role that elements of the Saudi government may have played in the attacks.

Fifteen of the 19 men who carried out the attacks were Saudi nationals.