9/11 20th anniversary: Victims' families tell Joe Biden release Saudi documents or stay away

US President Joe Biden is under pressure to release documents about 9/11 from families and frontline staff who say they don't want him at the 20th memorial unless he releases them. Photo / AP

More than 1000 people affected by the 9/11 terrorist attacks don't want US President Joe Biden to participate in 20th anniversary events unless he agrees to declassify evidence they believe will show a link to Saudi Arabian leaders.

Nearly 1800 of the victims' family members, first responders and survivors released the statement on Friday (local time), asking Biden to stay away from three sites where the attacks took place – in New York, Virginia and Pennsylvania - unless he releases the documents.

They believe the documents will confirm Saudi officials were involved in supporting the September 11, 2001 attacks on the World Trade Towers.

They argue Biden promised during his election campaign to be more transparent and to release as much information as possible.

"We cannot in good faith, and with veneration to those lost, sick, and injured, welcome the president to our hallowed grounds until he fulfils his commitment," the letter provided to NBC states.

"Since the conclusion of the 9/11 Commission in 2004 much investigative evidence has been uncovered implicating Saudi government officials in supporting the attacks," the statement says.

"Through multiple administrations, the Department of Justice and the FBI have actively sought to keep this information secret and prevent the American people from learning the full truth about the 9/11 attacks."

In particular, the group wants all documents related to a Federal Bureau of Investigation (FBI) investigation in 2016 that looked at the alleged Saudi links.

An unforgettable image of the devastating terrorist attack. Photo / Twitter

"Twenty years later, there is simply no reason – unmerited claims of "national security" or otherwise – to keep this information secret," the letter states.

"As we approach the 20th anniversary of 9/11, and having been used as a political bargaining chip for two decades, our patience has expired."

In this September 11, 2001 photo, a shell of what was once part of the facade of one of the twin towers of New York's World Trade Centre. Photo / File

They say that if Biden does not release the documents, they would be forced to object to any participation by the administration in memorial ceremonies.

Almost 3000 people were killed when terrorists hijacked four commercial planes and slammed them into the World Trade Centre, the Pentagon and a field in Pennsylvania.

It was the worst terror attack to take place on American soil.

Kris Boyson with his mother at the 9/11 memorial in New York in December 2019. Photo / Supplied