The US president said the US and its allies stopped a scheme after the 9/11 attacks in which attackers planned to use bombs hidden in footwear to enter the cockpit door of an aeroplane and fly it into the tallest building in Los Angeles.

"The plot was derailed in early 2002 when a southeast Asian nation arrested a key al-Qaida operative," Bush said in a speech on Thursday.

Last October, the Bush administration said there had been a plot to attack targets on the West Coast using hijacked aircraft, saying this was among 10 disrupted al-Qaida plots. Bush provided more details on Thursday.

He referred to the plot as targeting the Liberty Tower in Los Angeles, but White House aides afterwards said Bush had meant to say the intended target was the city's Library Tower.

Bush said that in October 2001, Khalid Sheikh Mohammed, the mastermind of the 9/11 attacks that year, had set in motion a plot for another attack inside the United States using shoe bombs to hijack an airplane and fly it into the tallest building on the West Coast.

Rather than use Arab hijackers as in the 11 September attack, Mohammed "sought out young men from southeast Asia whom he believed would not arouse as much suspicion", Bush said.