Lawyers for Saudi Arabia say a judge should reject claims by families of victims of the September 11 attacks that new evidence shows agents of the kingdom "directly and knowingly" helped the hijackers.
In papers filed in Manhattan federal court late on Friday, the lawyers said there is no evidence Saudi Arabia supported or caused the attacks.
They urged a judge to dismiss the claims against Saudi Arabia, saying the lawyers "have had enough chances to make their case".
Saudi Arabia was among the countries, companies and organisations sued in 2002 and afterward by families who claimed they aided Osama bin Laden and other terrorist groups.
The lawsuits sought billions of dollars in damages.
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Lawyers for Saudi Arabia also urged the judge considering the merits of the civil litigation to disregard claims by Zacarias Moussaoui, who is serving a life prison sentence after pleading guilty in April 2005 to conspiring with the hijackers to kill US citizens.
They called his comments to plaintiffs' lawyers last year "colourful but immaterial hearsay statements" from a convicted, mentally ill terrorist.
Before jurors spared Moussaoui's life, a psychologist testified for the defence at death penalty proceedings that he had paranoid schizophrenia.
Moussaoui said it was a lie that Saudi Arabia cut ties with bin Laden in 1994.
Lawyers for Saudi Arabia say the families are relying on the submission of "thousands of pages of inadmissible and irrelevant materials".
