"There was nothing from us in writing, but verbal undertakings were given" ... Richard Woolcott. Photo: Jon Reid

DEFENCE'S plans to develop the Cocos Islands in the Indian Ocean as a base for Australian and US spy drones and aircraft run counter to assurances Canberra has given the United Nations, one of Australia's most senior foreign policy figures has warned.

Australia promised it would not ''militarise'' the islands when persuading key nations at the world body not to oppose the transfer of the former British possession to Australian sovereignty, the former Department of Foreign Affairs and Trade secretary Richard Woolcott, said.

The recent Defence Force Posture Review suggested Defence consider upgrading the Cocos Islands airfield to support the new P-8 Poseidon maritime patrol aircraft likely to be acquired by the Royal Australian Air Force to replace its P-3C Orions.

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In March, The Washington Post reported the US was looking at the islands, in the north-east quadrant of the Indian Ocean, as a base to watch over a vast sweep of Asia.

The Cocos Islands were considered an ''ideal site'' to base not only manned US surveillance planes but also the Global Hawk, an unarmed high-altitude surveillance drone, the newspaper said. Spy flights could be launched over the South China Sea, scene of growing disputes between China and other countries with overlapping claims to marine and seabed resources.

The Australian posture review said Global Hawks could already operate from the Cocos Islands airfield, though the condition of the airfield and its limited infrastructure imposed constraints.

But Mr Woolcott recalls that when he was Australian ambassador to the UN in 1984, he gave Australia's assurances that the islands would not be converted to military purposes. ''There was nothing from us in writing, but verbal undertakings were given,'' he said yesterday.

The former chief diplomat writes in the Sydney Morning Herald today of his feelings of ''guilt'' at the way two ''crumbs from the British Empire's table'' that fell to Australia during his career were now being ''misused'' in ways that damaged Australia's standing in Asia.

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Militarising Cocos Islands will be betrayal, says former ambassador