Mr Jarrah was assigned to Saudi Arabia’s Washington embassy from 1999-2000 in Washington DC, and the US authorities believe that he oversaw assistance given to two al-Qaeda terrorists as they settled in the US before the attack.

The two al-Qaeda members, Khalid Al-Mihdhar and Nawaf Al-Hazmi, went on to hijack an American Airlines plane and kill 125 people after crashing into the Pentagon building.

It is the first time that the FBI has publicly confirmed that it suspects a link between the Saudi embassy in Washington and the September 11 hijackers.

The court document was filed by Jill Sanborn, the assistant director of the FBI’s counterterrorism division, and was alluding to findings in a heavily redacted FBI report when it mentioned Mr Jarrah.

The 2012 report identified two other Saudi men, Fahad al-Thumairy and Omar al-Bayoumi, who were suspected of assisting the hijackers, but it did not name Mr Jarrah, whom the FBI suspects was the “the third man» involved.

Saudi-arabiske myndigheter benekter anklagene, men faktum er at 15 av de 19 terroristene delaktig i 9/11 var saudi-arabiske statsborgere.

Amerikanske myndigheter har utad vært svært nøye med å sladde informasjon knyttet til rettssaken etterkommerne etter 9/11 står bak, og hevder at frislipp av informasjon kan true USAs sikkerhet. Men det kan også være et spill for galleriet og et ledd i å legge press på Saudi-Arabia.