President Obama had until midnight Friday to make good on his threat to veto a bill giving the families of 9/11 victims a chance to sue Saudi Arabia over alleged ties to the terrorist who carried out the attacks. (Associated Press Photo/Pablo Martinez Monsivais, File)

President Obama on Friday vetoed legislation that would allow families of 9/11 victims to sue Saudi Arabia over its alleged ties to the terrorists who carried out the attacks.

Congressional leaders plan to hold override votes in the coming days and supporters of the legislation say they are confident they can succeed in overturning the president’s action. It would be the first time during Obama’s presidency that Congress has overridden a veto.

The legislation would allow U.S. courts to waive claims to foreign sovereign immunity in cases involving terrorism on U.S. soil. The administration contends that this would break a longstanding practice that sovereign nations are protected from these types of legal threats. The result, according to the White House, is that American officials could now be sued in foreign courts over U.S. military or diplomatic actions abroad, which administration officials said poses a threat to national security.

“I recognize that there is nothing that could ever erase the grief the 9/11 families have endured. My Administration therefore remains resolute in its commitment to assist these families in their pursuit of justice and do whatever we can to prevent another attack in the United States,” the president wrote in his veto message to Congress. “Enacting [this legislation] into law, however, would neither protect Americans from terrorist attacks nor improve the effectiveness of our response to such attacks.”

But a group of families of 9/11 victims who have been advocating for the bill said in a statement Friday that they were “outraged and dismayed at the president’s veto,” rejecting “the unconvincing and unsupportable reasons that he offers as explanation.”

The bill passed the House and Senate without any dissents, but since that time several lawmakers have expressed misgivings about the measure — echoing the concerns voiced by the White House.

In a letter to his Republican colleagues Friday, House Armed Services Committee Chairman Mac Thornberry (R-Texas) argued that since the bill allows suits against officials whose countries have not been designated state sponsors of terrorism, it could lead to U.S. officials being forced to “disclose sensitive information” in reciprocal proceedings abroad, “even if none of the lawsuits against the United States were to be successful.”

White House spokesman Josh Earnest told reporters Friday that the administration has been “getting conflicting signals from members of Congress,” and was not sure if their concerns would lead them to vote against an override.

“The president’s not blind to the politics of this situation,” Earnest added, noting that opposing a bill championed by 9/11 families is “politically inconvenient.” But Obama is “willing to take some heat,” Earnest said, because the risks the bill poses to U.S. national security are too high.

White House press secretary Josh Earnest said that President Obama intends to veto a bill approved by Congress that would allow families of the victims of the Sept. 11, 2001 terrorist attacks to sue Saudi Arabia. (The White House)

Various national security experts and even the European Union’s delegation to the United States have weighed in with similar warnings in the last several days.

The override votes will likely take place next week.

“Now that we have received the veto message from the president, the Senate will consider it as soon as practicable in this work period,” said David Popp, a spokesman for Senate Majority Leader Mitch McConnell (R-Ky.).

Members are wary of voting against the wishes of 9/11 victims’ families, who insist that the legislation is necessary for them to stand a chance of suing Saudi Arabia over the alleged material support members of the Saudi government provided the attackers.

On Friday, a spokesman for Democratic presidential candidate Hillary Clinton said she would sign the legislation as president, CNN reported.

Saudi Arabia has strenuously argued that it had nothing to do with the attacks and the 9/11 Commission also said it did not find a connection.

“Saudi Arabia has long been considered the primary source of al Qaeda funding, but we have found no evidence that the Saudi government as an institution or senior Saudi officials individually funded the organization,” the commission’s report reads. Recently declassified pages from a 2002 congressional inquiry into the attacks also shed almost no new light on the issue.

Still, Saudi Arabia, which had already spent in excess of $3 million on lobbying this year, stepped up its efforts considerably this week as Congress braced for the president’s veto.

The kingdom added another three lobbying contracts to its roster, retaining the services of former Senate Republican Leader Trent Lott of Mississippi and former Democratic Sen. John Breaux of Louisiana as part of a $100,000 monthly contract with Squire Patton Boggs, according to documents filed under the Foreign Agents Registration Act. Saudi Arabia also filed FARA paperwork this week establishing a new contract with lobbying firm SGR worth $45,000 per month, and entered into an arrangement with the Glover Park Group for an as-of-yet undisclosed sum, according to filings.

Lawmakers who support the legislation have argued that if Saudi Arabia did nothing wrong, it should have nothing to fear in this law.

“This is a disappointing decision that will be swiftly and soundly overturned in Congress,” Sen. Charles Schumer (D-N.Y.), who co-author the legislation with Sen. John Cornyn (R-Tex.), said in a statement. “I believe both parties will come together next week to make JASTA the law of the land. If the Saudis did nothing wrong, they should not fear this legislation. If they were culpable in 9/11, they should be held accountable. The families of the victims of 9/11 deserve their day in court, and justice for those families shouldn’t be thrown overboard because of diplomatic concerns.”

Still, some members from both parties have called for Congress to delay its planned override vote so that lawmakers could try to renegotiate the bill with the White House.

“I hope that it can be put off, and cooler heads will prevail,” the Senate Intelligence Committee’s ranking Democrat, Dianne Feinstein (Calif.), said this week, calling efforts to move ahead with the bill in its current form “a mistake.”

The scope of the legislation was already narrowed once this year to respond to concerns raised by the administration and members of Congress.

Congressional leaders have indicated they are not interested in extending this process any longer.

“JASTA’s a fait accompli if it happens over the next week,” Senate Foreign Relations Committee Chairman Bob Corker (R-Tenn.), who has voiced concerns about the legislation, said Tuesday using the acronym for the bill. “Unless there are 34 people willing to fall on their swords over this, it’s probably not worth falling on your sword over.”

Karen DeYoung contributed to this report.