WASHINGTON: This frame grab from video shows the floor of the Senate on Capitol Hill yesterday, as the Senate acted decisively to override US President Barack Obama’s veto of Sept 11 legislation. – AP WASHINGTON: This frame grab from video shows the floor of the Senate on Capitol Hill yesterday, as the Senate acted decisively to override US President Barack Obama’s veto of Sept 11 legislation. – AP

WASHINGTON: The US Congress voted overwhelmingly yesterday to override Barack Obama's veto of a bill allowing 9/11 victims to sue Saudi Arabia, the first such rebuke of his eight-year presidency. The Senate overrode the veto in a 97-1 vote, followed a short time later by the House of Representatives, which knocked it down with a 348-77 vote, meaning the bill will become law. The rare act of bipartisanship was a blow to Obama, who lobbied hard against the bill, known as the Justice Against Sponsors of Terrorism Act (JASTA).

White House press secretary Josh Earnest called the Senate vote "the single most embarrassing thing" the legislative body has done in decades. "Ultimately these senators are going to have to answer their own conscience and their constituents as they account for their actions today," he told reporters traveling with Obama in Richmond, Virginia.

Coming in Obama's last months in office, the vote shows the White House to be much weakened. Obama has issued 12 vetoes during his presidency. None have been overridden until now, a rare feat given Republicans' longstanding control of Congress. His Republican predecessor George W Bush also issued 12 vetoes, of which four were overridden. The last president to avoid an override was the legendary Democratic congressional dealmaker - and former senator and congressman - Lyndon Johnson.

The White House argued the 9/11 bill would undermine the principle of sovereign immunity, opening up the United States to lawsuits. In a letter to Republican and Democratic Senate leaders obtained by AFP, Obama said: "I strongly believe that enacting JASTA into law would be detrimental to US national interests". Obama warned of "devastating" consequences for the Pentagon, service members, diplomats and the intelligence services. It would "neither protect Americans from terrorist attacks, nor improve the effectiveness of our response to such attacks," he warned. "The United States relies on principles of immunity to prevent foreign litigants and foreign courts from second-guessing our counterterrorism operations and other actions that we take every day."

Families of 9/11 victims have campaigned for the law, convinced 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 ties to the plotters. The bill's co-sponsor, New York Democrat Chuck Schumer, told senators it "would allow the victims of 9/11 to pursue some small measure of justice".

Behind the scenes, Riyadh has been lobbying furiously for the bill to be scrapped. A senior Saudi prince reportedly threatened to pull billions of dollars out of US assets if it becomes law, but Saudi officials now distance themselves from that claim. The US-Saudi relationship had already been strained by Obama's engagement with Saudi's foe Iran and the July release of a secret report on Saudi involvement in the 9/11 attacks.

The kingdom maintains an arsenal of tools to retaliate with, including curtailing official contacts, pulling billions of dollars from the US economy, and persuading its close allies in the Gulf Cooperation Council to scale back counterterrorism cooperation, investments and US access to important regional air bases. "This should be clear to America and to the rest of the world: When one GCC state is targeted unfairly, the others stand around it," said Abdulkhaleq Abdullah, an Emirati Gulf specialist and professor of political science at United Arab Emirates University. "All the states will stand by Saudi Arabia in every way possible," he said.

When Saudi Arabia wanted to pressure Qatar to limit its support for the Muslim Brotherhood group in Egypt, it spearheaded an unprecedented withdrawal of Gulf Arab ambassadors from Doha in 2014 and essentially isolated the tiny gas-rich nation within the GCC. When Sweden's Foreign Minister Margot Wallstrom strongly criticized Saudi Arabia's human rights record last year, the kingdom unleashed a fierce diplomatic salvo that jolted Stockholm's standing in the Arab world and threatened Swedish business interests in the Gulf. Sweden eventually backpedaled.

Chas Freeman, former US assistant secretary of defense for international security affairs and ambassador to Saudi Arabia during operation Desert Storm, said the Saudis could respond to this bill in ways that risk US strategic interests, like permissive rules for overflight between Europe and Asia and the Qatari airbase from which US military operations in Afghanistan, Iraq, and Syria are directed and supported. "The souring of relations and curtailing of official contacts that this legislation would inevitably produce could also jeopardize Saudi cooperation against anti-American terrorism," he said.

Fahad Nazer, an analyst at intelligence consultancy JTG and a former political analyst at the Saudi Embassy in Washington, said he'd be surprised if Saudi Arabia cut back counterterrorism cooperation since it's been beneficial for both countries. Still, relations with Washington had already cooled well before the 9/11 bill sailed through both chambers of Congress. The Saudis perceived the Obama Administration's securing of a nuclear deal with Iran as a pivot toward its regional nemesis. There was also Obama's criticism of Gulf countries in an interview earlier this year, despite their support for the U.S.-led fight against the Islamic State group in Iraq and Syria.

Joseph Gagnon, a senior fellow at the Peterson Institute for International Economics, said estimates put the figure of official Saudi assets in the government at somewhere between $500 billion and $1 trillion when considering potential foreign bank deposits and offshore accounts. The kingdom had $96.5 billion in holdings of Treasury securities in August, according to the most recent number released by the Treasury Department. Saudi Arabia ranked 15th in its holdings of US Treasury debt.

Gagnon, who previously worked at the US Federal Reserve Board and Treasury, said there isn't much realistically the kingdom could do to move against the dollar or other US assets "that would hurt us a tenth as much as it would hurt them." He said the US would actually welcome downward pressure on the dollar and questioned what other markets are big enough to absorb what they could sell. The US-Saudi Business Council's CEO and Chairman Ed Burton says business between the two countries will continue, though potential deals could be jeopardized by JASTA. "No business community likes to see their sovereign nation basically assailed by another nation," Burton said.

As one of the world's largest oil exporters with the biggest economy in the Gulf, Saudi Arabia also has other business partners to choose from in Europe and Asia, said President and CEO of the National US-Arab Chamber of Commerce David Hamod. "America is no longer the only game in town," he said. "No one knows how Saudi Arabia might respond to an override of President Obama's veto, but what's the point of calling the kingdom's bluff?"

The CEOs of DOW and GE sent letters to Congress warning of the bill's potentially destabilizing impact on American interests abroad. Defense Secretary Ash Carter this week sent a letter to Congress saying "important counterterrorism efforts abroad" could be harmed and US foreign bases and facilities could be vulnerable to monetary damage awards in reciprocal cases.

Such reactions may not come directly from Riyadh but countries connected to Saudi Arabia, said Stephen Kinzer, a senior fellow at the Watson Institute for International and Public Affairs at Brown University. He said the eight-decade-long US-Saudi relationship is "entering into a new phase," in which ties will be mostly underpinned by arms sales, unlike during the era of warm relations under President George W Bush. Abdullah, the Gulf analyst at UAE University, said he expects to see a GCC that acts more assertively and independently of the US in places like Yemen, Bahrain and Egypt. "This is not just a threat. This is a reality," he said.