In this 2009 photo, US President Barack Obama greets King Abdullah of Saudi Arabia before the official G20 leaders group photo with Britain's Queen Elizabeth II at London's Buckingham Palace. Image Credit: AP

Riyadh: Throughout US President Barack Obama’s time in the White House, Saudi Arabia and its allies in the Gulf have watched with dismay as the kingdom’s decades-old alliance with the United States seemed to be slipping.

Then came the overwhelming congressional support for Jasta, or the Justice Against Sponsors of Terrorism Act, which will allow relatives of those killed in the September 11, 2001, terrorist attacks to sue Saudi Arabia for any suspected role in the plot.

That was all the proof many Saudis needed that the alliance that has underpinned the regional order for decades was fraying — perhaps irreparably.

“Jasta is a wake-up call for the Saudis, that it is time to revisit the concept of the alliance with the United States,” said Khalid Al Dakhil, a Saudi political sociologist and writer.

Saudis responded to the passage of the bill, after both houses of Congress voted on Wednesday to override Obama’s veto, with a mix of anger and disappointment, while many have already begun thinking about how their country will need to adjust.

Passage of the law was a huge blow to relations with the Saudis, who have long maintained strong ties in Washington though close cooperation with the US government on a range of issues, from economic and oil policy to counterterrorism to shared intelligence and military programmes.

Saudi diplomats, and a range of public relations companies hired by the Saudi government, lobbied hard against the bill, with Adel Al Jubeir, the Saudi foreign minister and former Saudi ambassador to Washington, leading the effort. But that failed to persuade enough lawmakers to vote against a bill promoted by the families of victims of the terrorist attacks on September 11, 2001.

That resilient association of Saudi Arabia with the attacks angers many Saudis. Their government disowned Osama Bin Laden, a Saudi citizen, in 1994. Al Qaida, and more recently the terrorists of Daesh, have frequently targeted the kingdom, killing Saudi civilians.

Many question why suspicions of Saudi involvement in the September 11 plot persist in the United States, despite the passage of 15 years, a congressional investigation and the release this year of the long-classified 28 pages that were believed to contain evidence of complicity by Saudi officials. None of that has produced evidence of Saudi involvement, they say.

“Because the bill has been tied so strongly to 9/11 and Saudi Arabia, it helps feed this perception that Saudi Arabia is somehow responsible for Islamist terrorism,” said Faisal Bin Farhan, a Saudi businessman and chairman of Shamal Investments. “And that to me is more worrying than any direct effect of the law itself.”

On social media, some users suggested that the bill was part of a sinister conspiracy against the kingdom.

“America failed for 15 years to prove a role for the Saudi government in the 9/11 attacks, including in the congressional report and the 28 pages,” wrote Khalid Al Alkami. “#Jasta_Law Blackmail?”

“The goal of the Jasta law is to freeze the money of the Kingdom of Saudi Arabia and its sources and to paralyse its movement in Yemen and Syria while releasing Iranian money to tip the balance,” wrote Hutheifa Azzam.

Saudi and Gulf analysts said that the depth of the Saudi-US alliance gave the kingdom many ways to express its displeasure.

“It is certain that the strategic alliance between the two countries is in a real crisis,” Salman Al Dossari, the editor-in-chief of the Saudi-owned Al Sharq Al Awsat newspaper, said in an email. “If it is true that Riyadh shall be harmed by the crisis, Washington also has interests in the region, and they will definitely be affected as well.”

Saudi Arabia has lots of money invested in the United States, and Al Jubeir, the Saudi foreign minister, warned that such investments could be withdrawn if Saudi Arabia feared that its assets were in jeopardy of seizure as part of US legal proceedings. It remains unclear if Saudi Arabia will start withdrawing those assets.

The United States has a large military presence throughout the Gulf, with training missions in Saudi Arabia and large bases in Qatar, Bahrain and the UAE. The US also cooperates with Saudi Arabia in military operations in Yemen and elsewhere, as well as sharing intelligence for the fight against Al Qaida and the terrorists of Daesh.

“This situation, if exploited, would do a great deal of harm to US interests, let alone Riyadh’s effective cooperation in combating terrorism and the reflection of this on the war on terrorism as led by the US,” Al Dossari said.

Abdul Khaleq Abdullah, a professor of political science in the UAE, said that while the law appeared to be aimed only at Saudi Arabia, other countries in the region feared that it was only a matter of time before the US decided, “Let’s go after them, too.”

While 15 of the 19 hijackers who carried out the September 11 attacks were from Saudi Arabia, two were from the UAE, one from Lebanon and one from Egypt.

“There is thinking now more than ever that maybe the United States is not the safest place for future investments,” Abdullah said. “So eventually, maybe, we’ll have to stay away from the US and invest elsewhere.”

The alliance between Saudi Arabia and the United States goes back seven decades, to when King Abdul Aziz, the founder of the modern Saudi state, met President Franklin D. Roosevelt aboard the USS Quincy at the Great Bitter Lake in the Suez Canal.

Ties between the two nations have expanded enormously since then, as the United States has sought a steady supply of oil and a partner in the Arab world. Saudi Arabia has sought the security of protection from an international power.

Other links have developed as well. Tens of thousands of Saudi students attended schools in the United States, the Saudi government has invested billions of dollars in US military technology and the countries’ intelligence services have shared information on terrorist threats.

But tensions have endured, largely reflecting the difference in values between the nations.

The Saudi government watched in dismay as the United States tacitly encouraged the ouster of President Hosni Mubarak in Egypt during popular protests against him. The Saudis have tried and failed to overcome US reluctance to intervene more forcefully in the civil war in Syria. They opposed Obama’s push to reach a nuclear agreement with Iran, Saudi Arabia’s regional rival.

The September 11 law has left many analysts questioning the alliance’s future.

“The countries still need each other, but it does increasingly look like a marriage that is past its sell-by date,” said Michael Stephens, the head of the Royal United Services Institute Qatar. “Both sides are questioning the utility of being hitched together.”