London ? An al-Qaida operative who planned to bomb the World Bank in Washington and the New York Stock Exchange as well as other landmarks in the United States and Britain was sentenced to life in prison Tuesday.

Dhiren Barot, 34, a former airline ticket clerk and Muslim convert, was arrested in London in 2004 and pleaded guilty to conspiring to commit mass murder.

“You have chosen to use your life to bring death and destruction to the Western world,” Judge Neil Butterfield told an impassive Barot in a London courtroom. “You were planning to bring indiscriminate carnage, bloodshed and butchery … on a colossal and unprecedented scale.” His sentence provides the possibility of parole after 40 years.

According to prosecutors who read from Barot’s notes and computer files, Barot was pleased by the Sept. 11, 2001, attacks and planned to kill hundreds, if not thousands of people in the United States and Britain to create another “memorable black day for the enemies of Islam.”

Concern about his plots led President Bush to heighten security alerts and tighten security at financial buildings in the Northeast in 2004. British police seized documents that included detailed drawings of the World Bank, the International Monetary Fund and other buildings.

Prosecutors said Barot’s planned attacks in Britain were more imminent than those in the United States. He was drawing several plans for synchronized attacks in London, including blowing up a subway as it passed in a tunnel under the Thames River and exploding limousines loaded with gas cylinders near the Savoy, Ritz and other London hotels.

Prosecutor Edmund Lawson said Barot also kept documents in which he said he wanted to add napalm and nails to the bombs to “heighten the terror and chaos.”

“I quote Barot’s own words,” Lawson said. “‘Imagine the chaos that would be caused if a powerful explosion were to rip through here and actually rupture the river itself. This would cause pandemonium, what with the explosions, flooding, drowning, etc. that would occur.'”

Lawson said Barot made a detailed proposal to al-Qaida financiers in Pakistan, laying out, for example, that he wanted to use a six-man team to blow up the limousines.

“The fact that he wanted to do so many things at once was part of his downfall,” said Michael Clarke, a terrorism expert at King’s College in London. “It was so big that it would have been very difficult to carry out.”