U.S. President Joe Biden has thrown his support behind a “fresh review” of long-classified documents after families of 9/11 victims said he’s not welcome at the 20th-anniversary events unless the secret files are released.

The president said he approves of the Department of Justice reviewing the material, which families believe show Saudi Arabian leaders supported the attack that killed almost 3,000 people.

In a long-running legal battle by 9/11  family groups against Saudi Arabia, the Justice Department said the F.B.I. “recently” closed a portion of its investigation into the attacks. The department said the F.B.I was beginning a review of documents (that it had previously said must remain secret) with a view toward disclosing more [of the documents].

It is unclear what additional information will become public or when the public will see it. 

The move comes just days after a group representing more than 1,600 people directly affected by the attacks called on President Joe Biden to avoid any memorial events next month. 

The group said it would publicly protest against Biden if he does attend (a potential PR disaster for the American President), unless he fulfills a campaign promise to be more transparent with the families about the matter. 

Brett Eagleson, an advocate for the families and whose father Bruce was killed in the attacks says he would remain skeptical until the documents are released.

Eagleson said “we appreciate President Biden acknowledging our families today as we pursue justice and accountability against the Kingdom of Saudi Arabia. Unfortunately, however, we have heard many empty promises before."

In a letter, the victims’ families said they were hopeful Mr Biden would place truth, justice and accountability before the interests of the Kingdom of Saudi Arabia. 

The family groups renewed their push to have the 9/11-Saudi secret documents declassified after the release of an intelligence report in March that said Saudi Crown Prince, Mohammed bin Salman, approved the killing of Saudi dissident and journalist Jamal Khashoggi at the Saudi consulate in Istanbul. 

Fifteen of the 19 attackers were Saudi nationals. A 2004 9/11 commission report said charity groups in Saudi Arabia helped finance the attackers. 

Family groups say further evidence has emerged after the 2004 commotion that strongly hints at a Saudi connection. 

Following the attacks, the U.S. rushed into two devastating wars in Afghanistan and Iraq; under the pretext of fighting terrorism.