In a last-minute court filing this week, the US government moved to block the release of a trove of documents about the September 11, 2001, attacks to families of the victims. However, senior intelligence officials said they were unable to explain the reasons for the secrecy, as doing so would compromise US national security.

In its latest move to protect its relationship with the Saudi monarchy, the Trump administration has blocked the release of FBI files on the September 11 attacks that it has been deemed to contain information that would imperil US national security.

According to a report by ProPublica, the US Department of Justice claimed in a federal court filing late Monday night that the documents exposed state secrets, but said that it could not explain what those secrets involved, because that, too, is secret.

“This assertion of privilege is over highly sensitive and classified national security information concerning foreign government information; intelligence activities, sources and methods; and information concerning foreign relations and foreign activities of the United States, including confidential sources,” acting Director of National Intelligence Richard Grenell said in a sworn declaration given to the US District Court for the Southern District of New York.

“This information must be protected because its disclosure reasonably could be expected to cause serious damage, and in many cases exceptionally grave damage, to the national security of the United States,” Grenell said, according to the blog Florida Bulldog. His testimony was joined by those of US Attorney General William Barr and other leading intelligence officials.

“The extraordinary lengths that they’re going to here suggest that there must be some deep, dark secret that they’re still trying very hard to hide after almost 20 years,” Steven Pounian, a lawyer representing the September 11 victims’ families, told ProPublica.

“But who are they protecting? Something might be a Saudi government secret. But how can these be secrets that still need to be kept from the American people after all this time?”

The releases would have been part of a 2017 lawsuit against Saudi Arabia by the families of those who died in the September 11 attacks and the aftermath. On that day, 19 hijackers from the terrorist group al-Qaeda took over four US airliners and flew them into three buildings: the two World Trade Center towers in New York, which later collapsed, and the Pentagon in Arlington, Virginia, a portion of which burned; the fourth plane fell from the sky over Pennsylvania when the passengers attempted to retake control of it.

Of those 19 hijackers, 15 were from Saudi Arabia, and the mastermind of the operation, Osama bin Laden, came from one of the country’s wealthiest families.

Last September, Barr allowed the families to learn the classified name of one of the hijackers’ accomplices, but only under a strict vow of secrecy.

While the 9/11 Commission fact-finding probe between 2002 and 2004 officially found “no evidence that the Saudi government as an institution or senior Saudi officials individually funded” the attacks, it noted “the likelihood” that Saudi-sponsored charities did, AP noted. A 2016 law permitting Americans to sue foreign governments for acts of terrorism is what allowed the families’ lawsuit to go forward.

However, after a more recent barb in the US-Saudi relationship appeared in late 2018 when Saudi journalist and US resident Jamal Khashoggi was assassinated and dismembered in the Saudis’ Istanbul consulate, Washington similarly swept the issue under the rug, with US President Donald Trump finding himself at odds with the CIA in assigning blame for the murder.

"The United States has never - not once - put this relationship on the line over the fate, or the human rights, of any individual or group of individuals,” author and historian Thomas Lippmann told Sputnik in October 17, 2018, just weeks after Khashoggi disappeared.

“In fact, the Truman administration put a policy in writing that said exactly the opposite. It said: ‘We're there to do business and for reasons of security. We're not there to tell them how to run their country or organize their society.' That policy's never been rescinded, and that's what we have always done,” Lippmann said.