FBI agents, fire fighters, rescue workers and engineers work at the Pentagon crash site on September 14. Photo by Tech Sgt. Cedric H. Rudisil, US Armed Forces

The Chief of Army has extended sympathy on behalf of all Australian soldiers to Americans who have lost family and friends in the attacks on New York and Washington.

The Federal Government is preparing to assist the United States in fighting global terrorism.

Lt-Gen Peter Cosgrove said the attacks on the World Trade Centre and the Pentagon had "shocked us all".

"Many of us have served along side our colleagues in the US Armed Forces either on joint exercises, in liaison roles or as part of exchange programs," he said.

"The images that we saw days ago will haunt us forever, and the scale of death and destruction defies imagination.

"We grieve for those civilians and military personnel who have lost their lives in this terrible tragedy.

"On behalf of the men and women of the Australian Army we extend our deepest sympathy and condolences to the families and friends of these people. Our thoughts and prayers are with them during this very difficult time.

"The United States of America is a great and loyal ally. The Australian Army stands shoulder to shoulder with the US Armed Forces. We are ready to play whatever part necessary if we are called upon by the Australian Government to help the community of nations in dealing with this terrorist act and bringing the criminals responsible to justice."

The Government announced that the attacks fell under Article IV of the ANZUS Treaty, and as such, had invoked the treaty.

In accordance with Article IV, the Government would continue to consult closely with the US in relation to any response, militarily or otherwise, the US may deem appropriate.

The Minister for Defence, Peter Reith, said "The Government will respond to US requests for military support within the limits of our capability."

Mr Reith said the ADF had already commenced the provision of support to the United States in various areas:

HMAS ANZAC, currently serving as part of the international coalition enforcing United Nations trade sanctions on Iraq in the Persian Gulf, would extend its deployment until September 23.

The US requested that HMAS ANZAC's deployment be extended to assist the International Coalition and the US.

The US had emphasised the versatility and capability of HMAS ANZAC in maritime interception operations.

HMAS ANZAC's contribution to this operation was highly valued.

The ADF, in conjunction with Lockheed Martin, had conducted a C-130J Hercules flight in support of relief operations in New York.

The aircraft is in the US for software development as part of the C-130J acquisition project.

With emergency response personnel mobilised all over the US, the Government was asked to make the aircraft available to transport US personnel from Atlanta to New York.

RAAF personnel, currently on exchange with US forces, had been involved in flying combat air patrols over continental United States.

Mr Reith said ADF exchange personnel attached to the United States had been authorised to deploy with US forces on operations, both inside the United States and abroad.

There were 295 ADF personnel serving in the United States which includes embassy staff, trainees and personnel on courses - 75 RAN, 130 RAAF and 90 Army.

There were 82 ADF exchange personnel and 40 ADF Liaison officers serving in US units, of which 28 were available for deployment.

The ADF personnel deployed with US units performed a wide variety of duties in combat and combat support functions, including:

Pilots and weapons systems officers attached to fighter, bomber, tactical airlift and maritime surveillance units;

Army personnel attached to infantry, aviation and special forces units; and

Seaman officers, pilots and warfare officers attached to US naval vessels.

The Government was also assisting the US through our intelligence capabilities.

"Although we continue to pray that survivors are found, it seems clear that many Australians have been murdered in the terrorist attacks in the US," Mr Reith said.

"The Government is determined to play whatever part we can in bringing the perpetrators to justice."