The purchase was announced earlier this month after an exchange of contracts between Stockland and the private seller.

The financial details of the transaction remain confidential.

The land makes up a significant portion of the East Leppington precinct, a proposed new suburb, which has not been released for planning yet.

The site is 1.5 kilometres from the proposed Leppington railway station and on the east side of Camden Valley Way.

A spokesman for the Department of Planning and Infrastructure said a release date for the East Leppington precinct has not been scheduled.

He said the precinct was expected to include about 3000 new dwellings to house about 8000 people when fully developed and include two or three neighbourhood centres.

"Dwelling targets and infrastructure needs are refined during the precinct planning process, which includes extensive consultation with all stakeholders before land is rezoned for urban development," the spokesman said.

However, Stockland has said it expects the first settlements to be in the 2014 financial year, subject to planning approval.

"The remainder of the home sites will be released over the following 10 years," a Stockland spokesman said.

"There are also opportunities for further development in line with our 3-R strategy, which includes bringing retail, and retirement living, into our residential communities," he said.

Stockland chief executive, residential, Mark Hunter said East Leppington would be a new master-planned community for Sydney.

"The transaction further increases our geographic diversity and strengthens our presence in NSW," Mr Hunter said.

"We have now entered into another of our targeted, strategic corridors — a corridor which is clearly undersupplied.

"This community will help meet the strong demand for new, affordable homes in south-west Sydney.

"The size and scale of the project will allow us to provide a broad range of products, catering to all market segments.

"We look forward to working closely with the local councils, state government and nearby residents as we bring the project to life."