The White House today reversed a previous decision and offered to have national security adviser Ms Condoleezza Rice testify publicly under oath about the September 11th attacks before the 9-11 commission.
The White House released a letter to the independent commission from legal counsel Mr Alberto Gonzalez outlining the offer.
It also said it would make US President George W. Bush and Vice President Mr Dick Cheney available to speak before a joint private session of the full panel.
Both offers were on condition that they would not set a precedent under the constitutional separation of executive and legislative powers, an administration official said.
The offers follow bombshell allegations from former White House counter-terrorism expert Mr Richard Clarke that Mr Bush and his top aides ignored an urgent threat from al-Qaeda in the months before the attacks on New York and Washington.
The 10-member bipartisan commission investigating the hijacked airliner attacks had unanimously requested that Ms Rice testify publicly and under oath. Mr Bush had previously insisted on meeting privately with only the chairman and vice chairman of the panel.
Up to now, White House lawyers have claimed executive privilege and refused to let Ms Rice testify publicly based on a long-standing position that presidential advisers who have not been confirmed by the US Senate cannot give public testimony.