No dates, but Vic airport link on the way

A rail link between Melbourne's CBD and the airport is on the way, but Victorian Premier Denis Napthine won't say when.

Further details will be released with next month's state budget, he says.

The premier announced the planned electric train link between Melbourne's Southern Cross railway station and Melbourne Airport at the Victorian Liberal Party conference on Sunday.

It will run via an existing rail line through Melbourne's west, with a branch line to the airport.

Dr Napthine described the project as a "concrete promise" although he did not set dates for the start and anticipated completion of the project.

"What we are saying very clearly (is that) a coalition government will build the airport rail link," he told Fairfax Radio on Monday.

"That's what the people need to know, that's what we are telling the people, and that's what will be in the budget this year."

When pressed, Dr Napthine said he expected significant work would be completed in four years, ahead of the 2018 state election.

"The details will be in the budget, which is in May, but we will see action on these projects if we are re-elected this year," he said.