The process of buying a corridor for an east coast high-speed railway line would begin under a re-elected Rudd government, which will pledge $52 million over the next four years for a Sydney-Canberra-Melbourne line.

A Rudd government would also introduce legislation to protect a corridor for fast trains between Australia's two largest cities, and would establish a high-speed rail authority within six months to manage the project.

The money would not be enough to buy the required land, but Deputy Prime Minister Anthony Albanese said it would enable a start to building a line that could be operational within 17 years.

''There are some people that say this won't occur but wouldn't it be a tragedy if, as the economics of a project like this improve over time, it becomes impossible because the planning and foresight wasn't there,'' Mr Albanese said.