THE US military planned to test deadly nerve gas on Australian soldiers in far north Queensland during the Cold War, declassified documents reveal.

The Defence and Prime Minister's office files show that the US was strongly pushing then prime minister Harold Holt's government in the 1960s to allow tests of two of the deadliest chemical weapons ever developed -- VX and GB, better known as Sarin nerve gas.

The revelation airs this morning on the Nine Network's Sunday program.

It says the top secret plan involved allowing 200 mainly Australian combat troops to be aerially bombed and sprayed with the chemical weapons.

It's understood the Iron Range rainforest near Lockhart River in far north Queensland was the likely location for the tests.

Peter Bailey, a former senior official with Mr Holt, tells the program the request caused consternation in Canberra, and as far as he knows the tests never went ahead.

But he says planning was very advanced in the US, which wanted the operation to be kept secret because the weapons were illegal under international law.

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