A deal to fund Melbourne's Metro Rail project has edged closer, with Malcolm Turnbull signalling a willingness to hand over cash, but not until Victoria submits a rigorous business case.

The Prime Minister met with Premier Daniel Andrews in Melbourne on Thursday to formally discuss the state government's major projects wish list.

Victoria is demanding up to $6 billion for various infrastructure projects, including Metro Rail project and the Western Distributor road link, arguing on current predictions the state is expected to get just 9 per cent of the federal infrastructure carve-up - well below its 25 per cent share of Australia's population.

Mr Turnbull is believed to have used the meeting to reiterate a willingness to fund commuter rail projects, unlike his predecessor, Tony Abbott, who argued the Commonwealth should stick to its knitting by funding only roads.

Mr Turnbull on Thursday said he wanted to consider the infrastructure needs of cities in a "thoroughly non-ideological manner".

"We will support and indeed invest in infrastructure based on what it delivers analysed in a rigorous cost-benefit manner, without discriminating to one type of infrastructure or another," Mr Turnbull told the University of Melbourne's economic outlook conference in Melbourne.

But Mr Turnbull is also adamant there will be no money for the Metro project in the absence of a robust business case and rigorous benefit-cost analysis. Despite the positive tenor of the talks, the federal government has expressed concern about a lack of detail on the project, which will link the Sunbury line to the Cranbourne/Pakenham line with a new cross city tunnel.

Victoria is not expected to submit a business case until early next year, meaning a possible funding announcement for the project is unlikely to be formalised until at least the May 2016 federal budget.

A spokeswoman for Mr Andrews confirmed discussions had focused on funding arrangements for vital infrastructure projects for Victoria, including the Melbourne Metro.