Lawyers for victims of the September 11, 2001 attacks in New York say they have amassed new evidence that agents of Saudi Arabia "knowingly and directly" helped the hijackers.
They say they have obtained sworn testimony from the so-called 20th hijacker to support their claims in a lawsuit.
But the Embassy of Saudi Arabia in Washington said in a statement on Wednesday that Zacarias Moussaoui's claims come from a "deranged criminal" and there is no evidence to support them.
Lawyers wrote in papers filed Tuesday in federal court in Manhattan that their claims are supported by an "expansive volume" of previously unavailable US and foreign intelligence reports, congressional testimony, government reports and other information.
Saudi Arabia says results of the most investigated crime in history show no involvement by the Saudi government or officials.