By Richard Galpin
BBC correspondent in Athens
A one-day strike by Greece's largest trade union is expected to stop work at venues for this summer's Olympic Games.
Time is running out for work to be completed
Hundreds of thousands of workers from the General Confederation of Labour, including those in the construction trade, will strike for an 8% pay rise.
Public transport and ports will be paralysed and some banks will close.
But the major worry is another day will be lost on Wednesday in the race to finish building before the Games open in Athens on 13 August.
The International Olympic Committee has frequently warned that Athens cannot afford to lose even a single day after years of delays.
It is now predicted, for example, that the main stadium will not be completed until 20 July.
Both the building contractors and the Athens Olympic organising committee say they are not concerned about the strike as the time can be made up easily.
But the union has threatened further action if its pay demand is not met.