In a top-secret intelligence memo headlined 'Bin Laden determined to strike in the US', the President was told on 6 August that the Saudi-born terrorist hoped to 'bring the fight to America' in retaliation for missile strikes on al-Qaeda camps in Afghanistan in 1998.

Bush and his aides, who are facing withering criticism for failing to act on a series of warnings, have previously said intelligence experts had not advised them domestic targets were considered at risk. However, they have admitted they were specifically told that hijacks were being planned.

The news comes as unease about prosecution of the war in Afghanistan grows. British troops deployed near the eastern Afghan city of Khost failed yesterday to locate any of the al-Qaeda fighters who, it is claimed, ambushed an Australian SAS patrol.

Senior sources at the Ministry of Defence said yesterday that the al-Qaeda or Taliban fighters who were being pursued were numbered in 'tens'. Escape routes have been cut off by coalition forces, the sources said.

'There has been no combat. We have established a forward operating base and are now clearing the area,' said Lt-Col Ben Curry, spokesman for the Royal Marines at Bagram air base.

MoD sources also said that the mystery illness which has struck British troops at Bagram has been identified as the winter vomiting disease which swept Britain earlier this year. The disease is common around the world and is caused by poor sanitation and hygeine. One possibility is that food brought in by civilian contractors through Pakistan may be to blame.

An American operation in the east of Afghanistan has also been criticised after hundreds of troops deployed after a series of missile attacks on US troops in Khost failed to find the enemy or to prevent new attacks.

For the first time in the war on terrorism, which has pushed his popularity levels to almost unheard of heights, Bush and his administration are on the defensive. The White House has revealed that Bush asked for an intelligence analysis of al-Qaeda attacks within the US because most of the information presented to him over the summer focused on threats to targets overseas.

However, there are growing demands for an independent investigation. The intelligence services have already been heavily criticised for failing to act on a series of clues that might have led them to the hijackers.

Sources quoted by the Washington Post and ABC TV said that at least two names listed in a July 2001 FBI memo about an Arizona flight school had been identified by the CIA as having links to al-Qaeda. But the memo was not acted on or distributed to outside agencies.

And, while administration officials have said repeatedly that intelligence analysts never imagined that terrorists would use planes in a suicide attack, a 1999 report for the National Intelligence Council warned that fanatics loyal to bin Laden might try to hijack a jetliner and fly it into the Pentagon.

The memo received by Bush on 6 August contained unconfirmed information passed on by British intelligence in 1998 revealing that al-Qaeda operatives had discussed hijacking a plane to negotiate the release of Sheikh Omar Abdel Rahman, the Muslim cleric imprisoned in America for his part in a plot to blow up the World Trade Centre in 1993.

Plans for ousting the Taliban and dismantling the al-Qaeda network were already under way when the terrorists struck in New York and at the Pentagon. One option was to arm Afghanistan's Northern Alliance - a ploy eventually used successfully during the war last autumn.