A Muslim convert planned to detonate a dirty bomb and launch an attack on the London Underground, a court has heard.
Barot claimed he had not received funding or materials
Former Hindu Dhiren Barot, 34, from London, plotted "massive explosions" in the US and UK, aiming to kill hundreds.
Barot, who last month admitted conspiracy to murder, wanted to pack limousines with gas cylinders and also use a radioactive "dirty" bomb.
Lawyers for Barot have insisted that he had neither funding nor bomb-making materials at the time he was caught.
Barot, from Kingsbury in north-west London, described by prosecutors as "a member or close associate" of al-Qaeda is due to be sentenced on Tuesday.
"The plan was to carry out massive explosions here and in the USA, the principal object being to kill hundreds, if not thousands, of innocent people without warning," prosecutor Edmund Lawson QC told Woolwich Crown Court
Barot, who had been under surveillance by the security service MI5, was arrested by armed police in August 2004.
The BBC, The Times and the Associated Press news agency successfully challenged a judge's ruling that had threatened to prevent reporting of details from the court hearing.
Mr Lawson told the court Barot had been planning 11 September-style synchronised attacks in Britain, which could have involved a dirty bomb and a gas attack on the Heathrow Express train service.
He had also plotted to detonate a bomb under the River Thames to flood the Tube network and potentially drown hundreds of commuters, Mr Lawson added..
The prosecution said Barot had written: "Imagine the chaos that would be caused if a powerful explosion were to rip through here [London] and actually rupture the river itself.
"That would cause pandemonium, what with the explosions, flooding, drowning etc that would occur."
Other targets in Britain had included the Savoy hotel and mainline train stations, Waterloo, Paddington and King's Cross, the prosecution said.
Barot also planned to strike the IMF and the World Bank in Washington DC.
The New York Stock Exchange building and the Citigroup headquarters, as well as the Prudential building in Newark, New Jersey, were also among his targets.
Barot admired the Madrid train bombings and wrote he was bent on creating "another black day for the enemies of Islam and a victory for the Muslims", Mr Lawson said.
At the heart of Barot's plot was a scheme entitled "gas limos project", uncovered in a document signed by him and found in Pakistan, Mr Lawson said.
Barot had planned to fill limousines with gas cylinders and detonate them in underground car parks near financial institutions.
His plans for bombings in the US were initiated before the 11 September attacks, then shelved, but worked on as late as February 2004, Mr Lawson maintained.
These US plans were then used in the planning of synchronised attacks in the UK, he added.
"The gas limos project might be seen as the culmination of Barot's murderous plans.
"There were various possible methods of attack raised for consideration, including part of what was to be considered for the UK.
"They included parking limousines packed with explosives next to or underneath the target buildings, arson, by means of hijacked petrol tankers, or igniting gas cylinders and even possibly the use of an aeroplane."
The court heard how Barot had used false identities, and at least one false passport, and had only been caught because of a "meticulous and impressive" police operation with input from British, American and Pakistani intelligence.
The prosecution said Barot had first received training in the use of weapons and explosives in 1995 in a mountainous area near the disputed territory of Kashmir.