The White House has bowed to intense political pressure and will allow Condoleezza Rice to testify under oath before the independent commission investigating the 9/11 attacks.

The Bush Administration appeared to have been stung by allegations of a cover-up after it earlier cited "executive privilege" to block requests for Ms Rice, the President's National Security Adviser, to co-operate with the commission.

The panel has asked to hear from Ms Rice for a second time in order to explore discrepancies between her evidence and that of Richard Clarke, the former counterterrorism chief.

Last week Mr Clarke made a series of highly embarrassing allegations for President Bush, claiming that he refused to take the threat from al-Qaeda seriously until after the 9/11 attacks, and that he was obsessed with establishing a link between the atrocity and Saddam Hussein.

"I would like to have her testimony under the penalty of perjury," said the commission's chairman, Thomas H Kean, said yesterday.

Ms Rice has granted one, private interview to the ten-person commission, in February. Her evidence was not given under oath, and no transcript was made of what she said.

After the sensation of Mr Clarke's sworn evidence last week, the White House denied a request for her to appear a second time, although Ms Rice has given numerous media interviews about the investigation.

The volte-face by the White House opens the way for another dramatic day of evidence before the commission, though it is unlikely Ms Rice will be drawn into damaging admissions.

Today a White House spokesman, speaking on condition of anonymity, said that not only would Ms Rice testify in public and under oath, but the Mr Bush and the vice president Dick Cheney would also appear jointly before the full commission in a private session.

Mr Bush had previously insisted on meeting privately with only the chairman and vice chairman of the panel.

The Bush Administration made the concessions after it obtained written assurances from the commission that the concession will not set a precedent.

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