Authorities found a bomb in a phone booth near the heart of London's government district where Vice President Dan Quayle was scheduled to meet Tuesday with British officials.
Police suspect the bomb was planted by the Irish Republican Army (IRA), making it the second time in a month that the outlawed group apparently has managed to place an explosive near government buildings. The earlier device blew up, but nobody was injured.
Home Secretary Kenneth Baker said quick action by police "saved a great deal of destruction, damage, possibly even death."
There was no claim of responsibility, but the head of the anti-terrorist squad, Cmdr. George Churchill-Coleman, said the bomb bore all the earmarks of the IRA.
Tuesday's bomb, which Independent Television News said contained five pounds of the plastic explosive Semtex, was located after telephoned warnings prompted evacuation of Parliament Square and nearby government buildings.
Churchill-Coleman said a man with an Irish accent called a television station in the morning, gave a code word and said a bomb would go off within a half-hour in Whitehall, between Parliament Square and Trafalgar Square.
"The warning given this morning was deliberately vague and lacking in detail," he said. "The likelihood of causing death and injury to the public was high and to give so little warning was utterly cynical."
The U.S. Embassy said Quayle, who was ending a six-day European tour Tuesday, had not changed his schedule, which included stops at the Foreign Office and at the nearby residence of Prime Minister John Major. The bomb was found five hours before Quayle was due at the Foreign Office.
Major said his meeting with political leaders from Northern Ireland would go ahead:
"People in Northern Ireland have suffered these intrusions to their life for many years. They have continued resolutely on with their normal way of life. Nothing is going to stop the continuing talks I will have with the Northern Ireland leaders."
In Dublin, Ireland, the IRA released a statement saying the London meeting was "a cynical and cosmetic exercise which will do nothing whatsoever to address the central issue giving rise to this conflict." The statement made no reference to the bomb alert in London.
Semtex is often used in bombs planted by the IRA, which is waging a violent campaign to drive the British from Northern Ireland. Recently, the IRA has carried out a stepped-up bombing campaign in Northern Ireland and Britain.