AUSTRALIA'S close military alliance with the United States is to be further entrenched with the building of a high-tech communications base in Western Australia.

The Federal Government is about to approve the base after three years of secret negotiations with Washington.

The Age has been told the base, which will be built on defence land at Geraldton, will provide a crucial link for a new network of military satellites that will help the US's ability to fight wars in the Middle East and Asia. It will be the first big US military installation to be built in Australia in decades, and follows controversies over other big bases such as Pine Gap and North West Cape.

The deal has come to light amid heightened political debate over the alliance with the US and in the same week that the US finally told Australia it would not allow it 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.

A 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 provide frontline military units instantly with high quality intelligence information, graphics and maps. All this information will be carried in unbreakable codes.

The 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. More ground stations might be built at other locations in Australia, he said.

Dr Dorling said the base would have direct military significance and would be a military target, similar to the submarine communications base at North West Cape and the joint facility at Pine Gap with its missile early warning system.