Federal funding has been pledged for Brisbane's Cross River Rail project.

Prime Minister Malcolm Turnbull was in the city to announced $10 million will to go towards finalising the plans for the multi-billion-dollar underground rail link.

Mr Turnbull said the money would be spent on an analysis of options relating to the long-promised project, and possibilities to link it with other plans for a Brisbane Metro Subway System.

There has been no decision on any additional funding, but the business case for the $5.4 billion project has been handed to both Infrastructure Australia and the Infrastructure Department.

“For many years federal and state and local governments have tended to pass like ships in the night and they haven't worked together,” Mr Turnbull said.

“We're changing that.

“Brisbane is clearly is going to need a cross-river rail solution.

“What we need to do is ensure that we get the investment put in place.

“We have not made a decision on what additional funding will be provided.”

The $10 million federal contribution will be combined with $50 million already allocated by the Palaszczuk Government to establish the Cross River Rail Delivery Authority (CRRDA).

The plan is explained in the video below.