More than 3,000 family members of victims from the 9/11 terrorist attacks are calling on both Vice President Kamala Harris and former President Donald Trump to oppose any Middle East peace deal with Saudi Arabia until the U.S. government holds the country accountable for any role it might have played on Sept. 11.

In the letter first obtained by CBS News, the families point to 1999 video footage of a Saudi government agent “casing” the U.S. Capitol as proof of Saudi involvement. “60 Minutes” reported on the video for the first time in June.

“As you campaign to become the next President of the United States, we ask you to pledge that you will not endorse any Middle East peace deal involving Saudi Arabia unless it fully addresses the role of the Saudi Arabian government in the 9/11 attacks,” the letter reads. “Justice and closure for the victims and their families must be a priority in our foreign policy.”

The letter was organized by 9/11 Justice, an organization formed in 2022 to represent families of victims of the terrorist attacks in New York, Virginia and Pennsylvania. The group has sued the Saudi government and pushed the U.S. government to declassify all remaining documents about 9/11.

The Biden administration has been pushing for several agreements between the U.S. and Saudi Arabia that include defense guarantees and civil nuclear cooperation, as well as one to normalize relations between Saudi Arabia and Israel. 

CBS News has reached out to both the Harris and Trump campaigns about the letter and the families’ request for them to oppose a deal.

Fifteen of the 19 al Qaeda hijackers who flew planes into the World Trade Center, the Pentagon and a field in Pennsylvania were from Saudi Arabia, but potential links between the Saudi government and the terrorists remained shrouded in mystery for years. 

In 2016, a long-classified portion of a congressional inquiry known as the “28 pages” became public for the first time. The investigation found evidence that some of the hijackers “were in contact with, and received support or assistance from, individuals who may be connected to the Saudi Government.” 

In September 2021, Mr. Biden issued an executive order directing the release of more 9/11-related documents. 

Brett Eagleson, the president of 9/11 Justice, said the families got more clarity about Saudi Arabia’s role in the terrorist attacks after the video of Omar al-Bayoumi, whom the FBI said was a Saudi intelligence operative, was obtained by British police and unsealed in federal court in June.

Eagleson, who lost his father in the 9/11 attacks in New York, said he’s looking to shine a spotlight on their cause before the Sept. 10 presidential debate hosted by ABC News in Philadelphia.

“These two candidates for office are going to be debating for the highest office in our land, less than a hundred miles away from [New York City], the night before the 23rd anniversary of 9/11,” he said. “We think this is a critical issue. We think these two should address it. And we hope this pledge helps us do that.”

As a 2020 presidential candidate, Harris was critical of Saudi Arabia after the 2018 killing of journalist Jamal Khashoggi, and backed a 2019 Senate bill calling for a public report about it. In an August 2019 questionnaire from the Council on Foreign Relations, Harris said the Saudis have been “strong partners” on counterterrorism but said the U.S. should “fundamentally reevaluate our relationship” and “us[e] our leverage to stand up for American values and interests.”

Trump initially vowed “severe punishment” for Saudi Arabia if the country was behind the 2018 killing of Khashoggi, but soon changed his tune and frequently stressed the importance of the U.S.-Saudi relationship.

“[W]e may never know all of the facts surrounding the murder of Mr. Jamal Khashoggi. In any case, our relationship is with the Kingdom of Saudi Arabia. They have been a great ally in our very important fight against Iran,” he said in a statement in November 2018. The U.S. intelligence community concluded that Saudi Crown Prince Mohammed bin Salman was behind the killing, which he denies.

In July, the Trump Organization announced plans to build a new tower in Saudi Arabia, and spoke with the crown prince earlier this year, according to the New York Times. Trump has repeatedly touted the Abraham Accords he signed in September 2020, which aimed to normalize relations between Israel, the United Arab Emirates and Bahrain. 

9/11 Justice has criticized Trump for hosting the Saudi-backed LIV Golf Tour at his Bedminister golf club in New Jersey in 2022. Trump defended hosting the tournament, and said, “I’ve known these people for a long time in Saudi Arabia and they have been friends of mine for a long time.” His clubs have hosted several LIV events in the years since.

President Biden’s proposed bilateral deal between the U.S. and Saudi Arabia would require ratification from the Senate, a virtual impossibility before Congress recesses for the fall campaign season.

“If there’s any peace deal to be had that involves the United States and weapons sales or collective security agreements, none of that should happen until Saudi Arabia addresses and is held accountable for what it did 23 years ago,” said Eagleson.

Members of the 9/11 Justice group were also active leading up to the 2020 election, before the group was formed. They met with Trump in September 2019 to push for declassification of 9/11 documents to help with their civil suit against the Saudi government, though then-Attorney General Bill Barr invoked the state secrets privilege to keep the documents hidden from view. 

Mr. Biden also interacted with some members of the group when he was a candidate. As attorneys representing family members of 9/11 victims were in the middle of a lawsuit against Saudi Arabia, Mr. Biden sent a letter to their lawyers in October 2020 criticizing the Trump administration’s move to invoke the privilege regarding 9/11 related documents. 

Mr. Biden added he would direct his attorney general to examine each case where that privilege is recommended, and “err on the side of disclosure” when events in question occurred two decades or longer ago.