Summary：CANBERRA, April 12 (Xinhua) -- Australian Prime Minister Malcolm Turnbull has pledged five billion Australian dolla

CANBERRA, April 12 (Xinhua) -- Australian Prime Minister Malcolm Turnbull has pledged five billion Australian dollars (3.88 billion U.S. dollars) to help build the long-awaited Melbourne Airport rail link.

A train line linking the Melbourne Airport in Tullamarine to the Central Business District (CBD) has been a major talking point for decades, but Turnbull on Thursday said his funding promise would ensure it becomes reality.

"The time for talk is over. There have been countless reviews, reports and recommendations but Melbourne is still waiting for a service almost all of the world's great cities take for granted," Turnbull said at a press conference from the airport.

"This is the rail link that Melbourne, Victoria and the millions of people who use the airport every year demand and deserve."

Treasurer Scott Morrison said it was the single biggest piece of infrastructure funding to be announced in the upcoming Federal Budget for 2018.

However, the funding pledged by Turnbull will not be enough to cover the entire cost of the project with the Victorian Government needing to pour in another five billion AU dollars.

Daniel Andrews, premier of Victoria, in 2017 announced that his government wanted to build the link within a decade but would need federal government funding to do so.

Turnbull wrote to Andrews on Wednesday night, urging him to meet the funding commitment on the "iconic piece of infrastructure."

"We're already committed to a rail link to the airport and we're obviously happy to work with any Commonwealth Government on this project," Jacinta Allan, Victoria's Minister for Public Transport, told reporters on Thursday.

The federal government proposed four route options for the project involving tracks above and below ground.

However, Allan said the state government's plan for an airport rail link included fast rail to regional areas and it was "concerning" that only one of the four routes proposed would allow for that.

Construction on the project will begin as soon as the best route is chosen.

An estimated 60 million passengers will use the Melbourne Airport every year by 2030.

Traffic congestion in Melbourne has become a hot button issue in both state and federal politics but Turnbull said building the link would "slash travel times, bust congestion, boost the Victorian economy and create thousands of new jobs."

"We want the Victorian government to partner with us in a true 50:50 funding partnership to build and own this iconic piece of infrastructure. We also welcome the involvement of the private sector," he said.

Under the proposal, the federal government would own 50 percent of the rail link in return for funding it.

Turnbull's government in 2017 committed 30 million AU dollars for a business case for the rail line, a report that Turnbull said would provide a clear idea of the best route and an estimated final price.

Previous reports have found that the project could cost up to 15 billion AU dollars (11.64 billion U.S. dollars), meaning private investment could be required to make up for a government funding shortfall.

The project on Thursday received the support of both the federal and Victorian opposition, meaning that either incumbent government losing upcoming elections is unlikely to stop it from going ahead.