The move comes after many relatives, survivors and first responders came out against Joe Biden's participation in 9/11 memorial events if the documents remained classified.

US President Joe Biden has signed an executive order directing the FBI to declassify documents related to the 9/11 terrorist attacks.

The order, coming a little more than a week before the 20th anniversary, is a significant moment in a years-long fight between the government and victims' families over what classified information about the run-up to the attacks could be made public.

The families have long sought the information in hopes of implicating the Saudi government, with many coming out against Biden's involvement in 9/11 memorial events if the documents remained classified.

Speaking on Friday, the president pledged that his administration "will continue to engage respectfully with members of this community".

The executive order states: "The significant events in question occurred two decades ago or longer, and they concern a tragic moment that continues to resonate in American history and in the lives of so many Americans.

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"It is therefore critical to ensure that the United States Government maximises transparency, relying on classification only when narrowly tailored and necessary."

It directs the Justice Department, and other executive branch agencies, to begin the review and declares that all declassified information must be released over the next six months.

(Courtesy AP)

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