The $A 2.8bn fleet will be employed on NSW TrainLink services from Sydney to the South Coast, Blue Mountains, Central Coast and Newcastle.

The trains will be delivered between 2019 and 2024, allowing the withdrawal of V-Set trains and redeployment of the more modern Oscar EMUs on the Sydney Trains suburban network, replacing other life-expired rolling stock.

The contract will also include fitting out maintenance depot and ongoing servicing of the fleet, including cleaning.

The closing date for expressions of interest is September 15 and a formal invitation to tender will be issued later this year.

"We met with prospective manufacturers in May at an industry briefing and it was clear there was a lot of enthusiasm among manufacturers from Australia and overseas to be involved in this significant project," says NSW transport minister Mrs Gladys Berejiklian. "Buying proven technology from an established manufacturer ensures customers will be enjoying a more comfortable ride sooner than if brand new trains were commissioned from scratch, as the Waratah trains were."

The NSW government has not specified whether the new trains will be single or double-deck, although the preference for an off-the-shelf design suggests a single-deck train is the more likely option.