President Barack Obama vetoed a bill Friday that would allow family members of 9/11 victims to sue Saudi Arabia, pitting him against Congress and both presidential candidates on an emotionally charged matter.

The White House claimed the legislation could expose US diplomats and servicemen to litigation in other countries. Republican and Democratic leaders in Congress say they'll override Obama's veto next week.

Obama has now issued 12 vetoes. If successful, Congress' override would be the first of Obama's presidency.

Support for the "Justice Against Sponsors of Terrorism Act" ran high among lawmakers, who overwhelmingly passed the bill earlier this year after pressure from victims' groups. The bill would end foreign countries' immunity in the United States from lawsuits, allowing federal civil suits to go forward if the country is determined to have had a hand in a US terror attack.

In his veto message, Obama wrote he had "deep sympathy for the families of the victims of the terrorist attacks of September 11, 2001, who have suffered grievously."

But he maintained the legislation would seriously hurt US national security interests and cause harm to important alliances, saying it "would neither protect Americans from terrorist attacks nor improve the effectiveness of our response to such attacks."

He warned that the law would hurt the effectiveness of the administration's action against terrorism by taking questions of foreign states' involvement in terrorism "out of the hands of national security and foreign policy professionals and placing them in the hands of private litigants and courts."

Obama also said the move would open Americans abroad, especially those serving in the military, to prosecutions by foreign countries, since this would remove the reciprocal agreements that now protect both sides from such lawsuits.

He also pointed to complaints that allied nations have made about the measure. This legislation, he said, "threatens to limit their cooperation on key national security issues, including counterterrorism initiatives, at a crucial time when we are trying to build coalitions, not create divisions."

(CNN)