The application, placed on exhibition this week, states that the NSW government has "endorsed terms for the construction of a fourth coal terminal at the port should certain conditions be met".

The Newcastle Herald understands that amounts to an in-principle agreement to support the terminal, and that several options for the T4 loader are still being considered as part of the planning process.

The port corporation's application proposes increasing the size of the approved harbour swing basin, and moving it about 200 metres to the east, near the Ausgrid wind turbine.

"In support of the NSW Government's commitment to further development of export capacity within the port of Newcastle, [the port corporation] has made the decision to amend the location of the swing basin," the application says.

"These changes are required to facilitate further expansion of coal-loading facilities on Kooragang Island upstream of the swing basin."

The T4 loader, being planned by the Rio Tinto and Xstrata-backed Port Waratah Coal Services, could add 140 million tonnes a year to the Hunter's export coal capacity.

A project application for T4 has been lodged with the NSW Department of Planning.

The Herald reported in March that the Kooragang Island wind turbine could be removed to make way for the port expansion, and that Port Waratah Coal Services and Ausgrid were in discussions about the implication of the proposed swing basin.

A port corporation spokesman said yesterday the swing basin would enable vessels to sail to proposed berths.