President Obama vetoes 9/11 victims bill
US President Barack Obama has vetoed a bill that would allow families of 9/11 victims to sue the Saudi government.
President Obama said he felt "deep sympathy" for the families but that the law would be "detrimental to US national interests".
Saudi Arabia's foreign minister had warned that the bill could cause his government to withdraw US investments.
The country denies any involvement in the 2001 attacks which killed nearly 3,000 people.
Fifteen of the 19 hijackers that targeted the World Trade Center and the Pentagon were Saudi citizens.
If the bill became law, it would allow victims' families to sue any member of the government of Saudi Arabia thought to have played a role in any element of the attack.
Congress overwhelmingly passed the bill earlier this month following a campaign by relatives.
However it was known that President Obama had serious concerns about the bill and was unlikely to sign it into law.
The Obama administration argues that the legislation would remove the sovereign immunity that prevents lawsuits against governments, and could expose Americans to a legal backlash overseas.
Democratic Senator Chuck Schumer, who co-sponsored the bill, said he was "disappointed" and would press ahead and overrule President Obama's veto.
"If the Saudis did nothing wrong, they should not fear this legislation. If they were culpable in 9/11, they should be held accountable," said Mr Schumer.
In 2004 the 9/11 Commission Report found "no evidence that the Saudi government as an institution or senior Saudi officials individually funded the organisation".
Last year an inmate in US custody, Zacarias Moussaoui, claimed that a Saudi prince had helped finance the attack that flew passenger planes into the World Trade Center and the Pentagon.
A fourth plane crashed into an empty field in western Pennsylvania.
Saudi Arabia rejected the accusation, which it said was from a "deranged criminal" with no credibility.