Extended trading hours have been granted to pubs and clubs in Sydney during the World Cup when thousands of passionate soccer fans are expected to gather in the city.

With the first match - South Africa versus Mexico - due to be broadcast live at midnight (AEST) on Friday (0000 Saturday) on giant screens at Darling Harbour, police are issuing warnings against rowdy behaviour.

"We won't tolerate anti-social behaviour, we won't tolerate drugs, we won't tolerate flares," Superintendent Michael Fuller told reporters at the site on Wednesday.

"Any of that sort of stuff and you'll be locked up or thrown out."

Despite a state government admission that soccer fever and alcohol "don't mix", the official FIFA Fan Fest site at Darling Harbour will be licensed to sell alcohol between 4pm and 2am on days when matches are screened, through until July 12.

In addition, some nearby licensed premises have been granted extended trading hours for the duration of the World Cup.

"There's certainly normal trading around Darling Harbour and the CBD and a number of premises around Sydney have applied for extended trading hours and (police) have put on additional resources to meet those needs," Supt Fuller said.

"I can't give you information about percentages but certainly I know of some (venues) in this area that have been extended. But around this area there are already a number of premises that have extended trading hours."

The Darling Harbour venue, including a giant screen and floating downsized soccer field, is one of only six FIFA Fan Fest Sites around the world.

Supt Fuller said there would be two "managed areas" within the site selling alcohol and the venue could safely hold about 20,000 people.

"Soccer is one of those games that incites passion," Police Minister Michael Daley told reporters at the site on Wednesday.

"Passion and alcohol sometimes don't mix. So if you've had too much to drink or if you want to come in here, have too much to drink and behave like a fool, the police will arrest you and you will be charged."

Asked if ethnic tensions were a concern for organisers, Mr Daley said they would not be tolerated.

"We're not going to tolerate any tensions, frankly. A bad refereeing decision or your team losing is no excuse for causing trouble," he said.

"Historical ethnic tensions - again, no excuse for causing trouble."

The Darling Harbour site will be bounded by bollards and security fencing and overseen by riot police.

It is likely to be crowded all night on occasions when games are scheduled to kick off at 4.30am (AEST).

Government trains and buses will run extra services during the World Cup to transport fans to and from Cockle Bay and Tumbalong Park, where the matches will be screened.

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