http://news.bbc.co.uk/2/hi/americas/3583639.stmWhite House U-turn on 9/11 inquiry
The move is seen as a major change of position
The White House has bowed to pressure to allow National Security Adviser Condoleezza Rice to testify in public and under oath to the 9/11 commission.
Previously officials had insisted that Ms Rice could meet the Commission in private for unsworn conversations but not face a full hearing.
President Bush and Ms Rice said that her appearance would contravene the constitutional separation of powers.
The offer has been made on condition that it would set no precedent.
'Key witness'
"The president decided to overrule the lawyers. After the events of last week, the American people need a full and complete hearing," the official told the BBC.
Last week, a former presidential security adviser, Richard Clarke, said the Bush administration had underestimated the terrorist threat because of a fixation on Iraq.
He said President Bush had pressed him to find a link with Saddam Hussein's regime in the hours and days following the 11 September attacks.
The BBC's Justin Webb, in Washington, says the move is a U-turn of "breathtaking proportions".
Ms Rice is considered a key witness for the commission, which is looking into policy against the terror threat before 11 September 2001, and the response afterwards.
'Embarrassment'
Correspondents had warned that the issue threatened to become a major embarrassment to the Bush administration.
The White House has been fighting off charges that it neglected the possibility of attacks before the 11 September 2001 attacks in New York and Washington.
Both the commission head and relatives of the victims of the attacks had demanded that Ms Rice testify.