The fight over funding for Brisbane's $4.4 billion Cross River Rail project continues between the State and Federal Governments.

Prime Minister Kevin Rudd says he is willing to negotiate with Queensland to secure a deal.

The State Transport Minister Scott Emerson says the Federal Government has only committed to paying a quarter - and that is not enough.

"Kevin Rudd claims to be a Queenslander - well he's got to stop short-changing Queensland," Mr Emerson said.

"They know what our offer is.

"It's a lot of talk from Kevin Rudd today - let's see him be genuine and agree to a 50-50 deal."

Mr Emerson says that is what the State Government has offered.

"I'm happy to sign that - that's a genuine, fair offer from us."

Robert Dow from the lobby group Rail Back on Track says urban rail and public transport will be a key battleground in the federal election.

The Federal Coalition has not committed to any funding for the project.