Khalid Shaikh Mohammed, the alleged mastermind of the September 11 attacks, has reportedly told US interrogators that original plans called for hijacking 10 planes -- five on each coast of the United States.
Besides New York and Washington, the tallest tower in Los Angeles was also on a list of targets discussed by Mohammed and Osama bin Laden back in 1996, CNN reported quoting US government sources.
Arrested in Pakistan in March, Mohammed is now a US prisoner being held at an undisclosed location.
"Bin Laden's involvement was focused on making sure the plot was a success," FBI analyst Matt Levitt told CNN.
"It was more important to have four successful hijackings that would strike at our political, military, economic infrastructure, than have an attack where eight or ten planes were involved ... and be discovered and thwarted," he said.
Mohammed told his interrogators that at one point, the 9/11 attacks were to include 22 hijackers on four aircraft, followed by a second wave of attacks that was to have received help from al Qaeda allies in Southeast Asia.
Government sources told CNN that US investigators still believe Mohammad Atta was the ringleader for the operation and "gave the 'go' signal" for the hijackers to deploy.
Officials also said Mohammed claimed he had never heard of Omar Bayoumi, a Saudi who provided rent money and other assistance to two of the hijackers in California, said the sources.
According to them, however, Mohammed would not necessarily have known the names of all the members of support cells.
US officials also told CNN that Jemmah Islamiyah leader Hambali, who was the most wanted man in Southeast Asia till his arrest recently, has told his American interrogators about a plot to attack two large hotels in Thailand during an upcoming meeting of Asian and Pacific leaders, including US President George W Bush.
Among other terrorist attacks, Hambali is accused of orchestrating the Bali nightclub bombings in October 2002, which left 202 people dead, most of them young tourists.