He and other defense lawyers said that rather than supporting Al Qaeda, the Saudis were sworn enemies of its leader, Osama bin Laden, who was exiled from Saudi Arabia, his native country, in 1996. “It’s an absolute tragedy what happened to them, and I understand their anger,” Mr. Kellogg said of the victims’ families. “They want to find those responsible, but I think they’ve been disserved by their lawyers by bringing claims without any merit against the wrong people.”

The Saudi Embassy in Washington declined to comment.

Two federal judges and the Second Circuit Court of Appeals have already ruled against the 7,630 people represented in the lawsuit, made up of survivors of the attacks and family members of those killed, throwing out the suit on the ground that the families cannot bring legal action in the United States against a sovereign nation and its leaders.

The Supreme Court is expected to decide this week whether to hear an appeal, but the families’ prospects dimmed last month when the Justice Department sided with the Saudis in their immunity claim and urged the court not to consider the appeal.

The Justice Department said a 1976 law on sovereign immunity protected the Saudis from liability and noted that “potentially significant foreign relations consequences” would arise if such suits were allowed to proceed.

“Cases like this put the U.S. government in an extremely difficult position when it has to make legal arguments, even when they are the better view of the law, that run counter to those of terrorist victims,” said John Bellinger, a former State Department lawyer who was involved in the Saudi litigation.

Senior Obama administration officials held a private meeting on Monday with 9/11 family members to speak about progress in cracking down on terrorist financing. Administration officials at the meeting largely sidestepped questions about the lawsuit, according to participants. But the official who helped lead the meeting, Stuart A. Levey, the under secretary for terrorism and financial intelligence, has been outspoken in his criticism of wealthy Saudis, saying they have helped to finance terrorism.

Image A German intelligence report described bank transfers made in the early 1990s by Prince Salman bin Abdul Aziz and other members of the Saudi royal family to a charity that was suspected of financing militants activities in Pakistan and Bosnia. Credit... Amel Emric/Associated Press

Even if the 9/11 families were to get their trial in the lawsuit, they might have difficulty getting some of their new material into evidence. Some would most likely be challenged on grounds it was irrelevant or uncorroborated hearsay, or that it related to Saudis who were clearly covered by sovereign immunity.