You would have risked shutting down the American civil aviation system with such generalised information

Condoleezza Rice

In a White House briefing, US National Security Adviser Condoleezza Rice said the information passed to President George W Bush was very generalised and did not relate to the possibility of attacks on buildings.

The disclosure of the 6 August briefing has sparked the biggest row in Congress since the attacks, with Democrat leaders asking whether the president could have headed them off.

But US Vice-President Dick Cheney hit back at the administration's critics, saying that some of their comments had been "thoroughly irresponsible and totally unworthy of national leaders in a time of war".

About 3,000 people died in the 11 September attacks

Ms Rice told reporters the main concern was over possible attacks on American interests overseas.

"I don't think that anybody could have predicted that these people would take an aeroplane and slam it into the World Trade Center, take another one and slam it into the Pentagon," she said.

The attacks on New York and Washington, which killed about 3,000 people, are thought to have been masterminded by Osama Bin Laden's al-Qaeda network.

'No intelligence lapse'

Ms Rice revealed that counter-terrorism officials met almost daily in the summer of 2001 to evaluate the threats.

Cheney: Investigation should not interfere with efforts to prevent attacks

She said US airlines had been specifically warned in August that terrorist groups were developing ways of carrying out hijackings, using disguised weapons such as mobile phones and key chains.

But there was no specific warning, she insisted, and to make public such threats might have meant closing down the country's entire aviation industry.

Ms Rice denied there had been an intelligence lapse, saying the US had successfully foiled attacks on Rome, Turkey and Paris as a result of its intelligence efforts.

Deep concerns

But BBC Washington correspondent John Leyne says Ms Rice's comments are unlikely to end criticism of the government.

I think we need to investigate what happened before to correct anything that went wrong so that in the future it would not happen again

Democrat Congressman Eliot Engel

Senate Majority leader Tom Daschle, of the Democrats, said he was "gravely concerned", and asked President Bush to hand over to Congress all the information he had received.

"Why did it take eight months for us to receive this information? And secondly, what specific actions were taken by the White House in response?" Senator Daschle asked.

Congressman Eliot Engel denied the Democrats were trying to make political capital from the affair.

"I don't think that we need to investigate what happened before for the sake of making a political point," he said.

"I think we need to investigate what happened before to correct anything that went wrong, so that in the future it would not happen again."

Congressional inquiry

A joint congressional investigation is due to begin hearings next month on the intelligence community's handling of the 11 September attacks.

An investigation must not interfere with the ongoing efforts to prevent the next attack

Dick Cheney

The White House has said that it will co-operate fully with the investigation. Mr Cheney warned that investigations into intelligence failings could put at risk efforts to prevent another attack.

"The president and I believe that one of our most important responsibilities is to do all that we can to ensure that an attack like 11 September never happens again," said Mr Cheney.

"An investigation must not interfere with the ongoing efforts to prevent the next attack, because without a doubt a very real threat of another perhaps more devastating attack still exists."

Flying school warning

The FBI's failure to react to a warning from one of its own agents has also been questioned.

A memo sent last July from its Arizona office is reported to have warned that groups like al-Qaeda might have sent students to flying schools in the US - the very places where the 11 September hijackers trained for their operation.

Even though the memo was reviewed, the FBI did not take any action on its central recommendation - that flight school records and visa applications by foreign students be cross-referenced.