AUSTRALIA'S close defence alliance with the United States is to be further entrenched with the building of a new US military communications base at Geraldton in Western Australia.

The Age has learned that the US is to build the base, which follows three years of secret negotiations with Canberra.

The base will provide a crucial link for a new network of military satellites that will help America's ability to fight wars in the Middle East and Asia.

It is the first big US military installation to be built in Australia since the controversy surrounding the joint spy base at Pine Gap more than two decades ago.

It will provide a key link in the system that will carry orders and intelligence information to US and allied troops on operations in the world's hotspots.

Details of the deal emerged on the same day as the US finally told Australia it would not allow even its key allies, including Australia, to buy its best fighter aircraft, the F-22 Raptor.

The base, about 370 kilometres north of Perth, will control two of five geostationary satellites — those with the highest priority parked over the Indian Ocean to monitor the unstable Middle East. Building may start within months.

Visiting fellow at the Australian Defence Force Academy Philip Dorling said that once the base was operating, it would be almost impossible for Australia to be fully neutral or stand back from any war in which the US was involved.

The network will be the military equivalent of the new generation 3G mobile phone system and will provide front-line military units instantly with high quality intelligence information, graphics and maps.

Defence Minister Brendan Nelson confirmed that talks were continuing with the US Defence Department which wanted to build a ground station for its Mobile User Objective System, an array of satellites being developed to provide new generation communications for US and allied forces.

The network is intended to significantly improve communications for fast moving ground troops.

Dr Nelson said the ground station would be built on defence land. More ground stations might be built at other locations in Australia, he said.

He said the Government would ensure that it had full knowledge of all activities at the ground station.

He said negotiations began in 2003 and were continuing. Details would be made public once the details were finalised.

Dr Nelson provided the information in response to a written question from Labor backbencher Daryl Melham.