The organisers of Pride in London have asked attendees to be "vigilant" after the shootings at a gay nightclub in Orlando.
Concerns for the London event were raised after lone gunman Omar Mateen, 29, left 49 victims dead at the Pulse nightclub in the Florida city.
Organisers of the London celebration for the LGBT community have insisted they are working closely with police and are reviewing the security situation.
On Monday, hundreds of mourners gathered in the heart of London's LGBT community for a vigil to commemorate the victims.
Old Compton Street in Soho fell silent at 7pm as a sign of respect for the slaughtered revellers, and candles, flags and flowers were laid at nearby St Anne's churchyard.
Earlier in the day at the launch of Pride in London's No Filter campaign, mayor Sadiq Khan insisted he was "not complacent" about the threat of a similar attack and said he was working to keep Londoners safe.
In two tweets, the official Pride in London account responded to a question about security at the event saying: "We continue to review situation with the police and security to provide a safe event. We ask everyone to be vigilant.
"As a large scale event we work with the @metpoliceuk who continue to assess intelligence and plan accordingly."
Pride in London is a two-week festival from June 10 and more than a million people are expected to attend events which culminate in a parade in London's West End on June 25.
A minute's reflection will be led from the main stage in Trafalgar Square after the parade and Pride in London's chairman Michael Salter-Church said attendees would "stand united in a moment of solidarity, peace and remembrance".
The Metropolitan Police's hate crime lead, Commander Mak Chishty, said the force has a "current robust, visible policing plan" for the Pride events.
He encouraged the LGBT community to report any fears but said: "There has been no specific threat whatsoever, the level of threat has not changed."