Dhiren Barot, 34, was sentenced at Woolwich crown court on Tuesday after pleading guilty to conspiracy to murder.
As he handed down the sentence, judge Neil Butterfield said: "You are ... a determined and dedicated terrorist, a highly intelligent and extremely dangerous man.
"This conspiracy was designed to strike at the very heart of democracy and the security of the state."
Barot was accused of also plotting to blow up the headquarters of Citigroup, the International Monetary Fund, the World Bank and Prudential in New York, Washington and Newark, New Jersey.
In Britain, Barot conceived of a so-called Gas Limos Project, a scheme to explode three stretched limousines packed with gas cylinders in car parks underneath major buildings.
Prosecutors said he carried out reconnaissance on leading London hotels and three railway stations.
The plan was discovered in a file named Eminem2.doc on a laptop found by Pakistani police in July 2004 after they arrested Naeem Noor Khan, described by police as a major al-Qaeda figure.
Scotland Yard said Barot's capture was a victory against terrorism.
"The conspiracy was in its final stages"
"For well over two years we have been unable to show the British public the reality of the threat they faced from this man. Now they can see for themselves the full horror of his plan," said Peter Clarke, the head of Scotland Yard's anti-terrorist branch.
Barot had planned to blow up an underground train as it passed through a tunnel below the River Thames - as part of a plot to unleash a "memorable black day" of terror, prosecutors said.
Prosecutors said the British attacks were "imminent" after Barot put the US plot on hold after the September 11 attacks.
"The conspiracy was in its final stages," prosecutor Edmund Lawson said.
Lawson said Barot also wrote in documents that he wanted to add napalm and nails to the limousine bombs to "heighten the terror and chaos".
He also considered adding radioactive material but decided a dirty bomb should be used in a separate attack, Lawson said.
Barot also planned to bomb the
Under the alias Issa al-Britani, Barot was named by the US commission investigating the September 11, 2001 attacks, as an associate of Khalid Sheikh Mohammed, the alleged mastermind.
Born in the Indian state of Gujarat, Barot's parents moved to England when he was one-year-old and settled in the northwest London suburb of Kingsbury, his father working as a banker while his mother worked at a local supermarket.
He left school at 16 and at 20 left the family home, converting to Islam.
Barot gained a qualification in tourism, and decided to go travelling, heading to Pakistan for the first time in 1995 as well as Afghanistan, Kashmir, Thailand, Singapore and other countries.