IT IS being billed as a ''football extravaganza'': a way to entertain tourists and Sydneysiders alike, as well as a golden opportunity to market the city to the world's soccer fans.

But NSW taxpayers are underwriting the cost of operating giant screens, which will show World Cup matches as well as sponsors' advertisements, to the tune of $7 million.

On the ball ... an artist's impression of Darling Harbour's Fan Fest.

During the month-long tournament, 1 million people are expected to attend the ''Fan Fests'' - cordoned-off areas of Darling Harbour and nearby Tumbalong Park, which the state government and soccer's governing body, FIFA, are operating jointly.

FIFA's share of the cost of running the free events extended to providing ''basic infrastructure'' such as the three screens that would float on the harbour and one in the park, a FIFA spokeswoman, who declined to go into more details, said.