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
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.
We have given Transport for London and the bus operators almost a year to resolve this issue.