The London Marathon will go ahead on Sunday as planned despite the two huge explosions at Monday's Boston marathon.
But security arrangements for the event and for former British prime minister Margaret Thatcher's funeral on Wednesday are being reviewed.
British Sports Minister Hugh Robertson said he is "absolutely confident" the London race, involving about 37,500 competitors, can be kept safe.
London has "enormous experience" in delivering major events, and the UK has some of the best security professionals in the world, he told the BBC just 12 hours after the blasts. He said he was horrified by the Boston blasts. "This is one of those instances where the best way to show solidarity with Boston is to continue," he added.
Home Secretary Theresa May has been briefed on the bombings by Scotland Yard Assistant Commissioner Cressida Dick and MI5 chief Sir Jonathan Evans, according to media reports.
The current threat level to the UK from international terrorism, set by the Joint Terrorism Analysis Centre, remains at substantial. The Metropolitan Police are reviewing security preparations for the London Marathon and for Thatcher's funeral.