Sports Minister Hugh Roberston said he was confident of security arrangements for the London event and encouraged people to attend as a show of solidarity with the US city that was rocked by two blasts near the finish line on Monday.
"In security terms we are as confident as we possibly can be that we can deliver a safe and secure marathon," Robertson told the BBC.
The 26-mile London Marathon will attract 36,000 runners, among them Britain's double Olympic champion Mo Farah, starting at Greenwich Park and winding through city landmarks before finishing at the Mall.
There will be a period of silence lasting 30 seconds ahead of the start to mark the "tragic events" in Boston, London organisers said in a statement.
"What happened in Boston was shocking and horrific and our thoughts are very much with the victims and their families," London Mayor Boris Johnson said while on a visit to Dubai.
Monday's blasts detonated close to spectators standing behind roadside barriers. The two explosions were about 50 to 100 metres apart as runners crossed the finish line.
The incident evoked memories of the September 11, 2001 attacks on the United States although no one has claimed responsibility and a political motive has not yet been determined.
Robertson said the British police and military had great experience in guarding big events.
"The best way of dealing with this is to get out on the streets to show solidarity with the people in Boston, to celebrate a fantastic marathon and send out a very clear message to those responsible we won't be cowed by this kind of behaviour," he added.
Metropolitan Police chief superintendent Julia Pendry said the force was reviewing its security arrangements in liaison with race organisers.
London police will also mount a sizeable security operation for the funeral of former Prime Minister Margaret Thatcher on Wednesday.
Mayor Johnson said he had talked to the London police commissioner about both events.
"We have got the funeral and then obviously we have got the marathon at the weekend...clearly we will be calling on the public to be vigilant and maybe there will be some intensified search operation but certainly we will be proceeding as normal," he added.
The London race was first run in 1981 and has become a centrepiece of the sporting calendar in Britain with elite athletes joined by a vast number of amateur runners who compete to raise money for charity.
Hundreds of thousands of people line the course with music and food stalls adding to the party atmosphere.
London Marathon chief executive Nick Bitel said he was saddened and shocked by the bloodshed in Boston.
"Our immediate thoughts are with the people there and their families. It is a very sad day for athletics and for our friends and colleagues in marathon running," Bitel said.
Hamburg's annual marathon will also go ahead as planned on Sunday after German police and security officials said they saw no increased risk for the event.
- Athletics, Track & Field