There were said to have been rows behind closed doors as members of the commission's staff objected to the way information about Saudi Arabia was being handled.

In December 2002, a year after the attacks, the House and Senate intelligence committees published a report on the US investigation into the attacks that was considered to largely clear the Saudis of the blame.

But President George W Bush ordered 28 pages of that report be classified to protect the methods and identities of US intelligence sources.

Campaigners have since alleged that it contained information implicating Saudi officials in supporting or funding al-Qaeda.

The issue of alleged Saudi involvement in the attacks has been repeatedly resurfaced amid attempts to allow victims' families to sue Saudi Arabia.

Now, President Barack Obama's administration is considering whether to release the pages and has indicated a decision will be made by June.

Earlier this week Saudi Arabia said it was confident nothing in the 28 pages implicates its leaders.

Saudi foreign minister Adel al-Jubeir, speaking in Geneva, said: "Our position since 2002, when this report first came out, was release the pages. We know from other senior US officials that the charges made in the 28 pages do not stand up to scrutiny."