Thousands of bus workers in London have voted by a majority of nine to one to go on strike in a row over payments to work during the London 2012 Olympic Games, said Unite.
Members of the Unite union backed industrial action by more than nine to one, raising the prospect of crippling walkouts during the Games, which start in the capital in July.
The union will decide in the coming days whether to name strike dates following the ballot result.
The union had previously called for a £500 payment to recognise the "massive increase" in workload during the Games this summer, saying that 800,000 extra passengers are expected to travel on buses.
Unite pointed out that other transport workers, including those on London Underground, London Overground, Docklands Light Railways, Network Rail and Virgin, will receive hundreds of pounds in extra payments during the Olympics.
The union called on London Mayor Boris Johnson to intervene in the dispute to remove the threat of industrial action in the run-up and during the Games.
Unite said it was giving the bus companies a final opportunity to consider the "landslide" ballot result before announcing possible strike dates early next week.
The union said bus workers were the only London transport employees not receiving an award for their extra effort during the Olympic Games.
At least 800,000 extra passengers are predicted to use London's buses during the Olympics, said Unite.
Regional officer Peter Kavanagh, said: "There are only seven weeks until the Olympics and the whole world is watching London. It's a disgrace that London's mayor, Boris Johnson, and the bus companies have allowed this dispute to get this far.
"Our members are only asking for an extra £17 a day which will just about buy you a pint of beer and a portion of fish and chips at the Olympics.
"Our members want the Games to be a success but their patience has run out."