The planned multi-million-dollar Parramatta light rail project is expected to be built in two stages, reflecting a growing priority within government for a new metro line linking Sydney's central business district and the west.

Instead of constructing the light rail line in one fell swoop as originally planned, sources say there is now a push within the transport bureaucracy to defer the construction of a section of the line between Camellia and Strathfield.

A change in tack would mean the first stage to be built would be from Westmead to Carlingford via Parramatta and Camellia.

The Baird government gave the green light late last year to a corridor for a 22-kilometre light rail line stretching from Westmead to Strathfield via Parramatta and incorporating Carlingford, Camellia and Olympic Park. However, the exact route remains under consideration and is not expected to be unveiled until early next year.