Sydney Airport Holdings Ltd has first right of refusal to build the A$5 billion ($3.7 billion) airport, which the government hopes will boost inbound air passenger numbers to Sydney by about a quarter, or 10 million people per year.

The new airport is the centrepiece of Prime Minister Malcolm Turnbull's A$30 billion national public works drive designed to keep Australia's economy ticking over as a decade-long resources spending boom unwinds.

Its location, at Badgery's Creek in Sydney's western outskirts, was first mooted in 1946 as the limits of the first airport - hemmed in by suburbs and the sea in the city's east - became clear.

The project has been bogged down in partisan debate over aircraft noise, funding and alternative sites ever since.

"The need for an airport in western Sydney has been screamingly obvious for many years," Turnbull told reporters in Sydney.

"We are getting on with the job, and this airport will be built ... it will become a catalyst for investment and industry in western Sydney. That is where Sydney's growth is," he said.

The airport's proposed 3,700-metre (2.3 miles) runway will be able to accommodate large Airbus A380 aeroplanes, said Australian Infrastructure Minister Paul Fletcher.

A spokeswoman for Sydney Airport, Joeley Pettit, had no comment on whether the company would opt to build the new project or contribute an anticipated A$1 billion toward its construction.

The company must exercise its option within four months of receiving formal notice from the government, which Fletcher said would happen before Dec. 31.

The project is set for completion in the mid-2020s, with Sydney's existing airport approaching maximum capacity, the government said in a statement.

(Reporting by Tom Westbrook; Editing by Paul Tait)