War games send wrong message: Greens

A joint military exercise with the US in central Queensland should be canned as it harms Australia's independence and sends the wrong message to our neighbours, a Greens senator says.

Acting Greens leader Scott Ludlam says the exercise, involving 30,000 Australian and US defence personnel, is about "expeditionary wars and invasions" and has backed peace activists' trespassing on to the training site at Shoalwater Bay.

"Most people join the ADF expecting that they're there for the defence of Australian territory," he said outside a peace conference in Brisbane on Thursday.

"That's not what they are training for - it's about landing on beaches and invading other people's countries.

"I don't think we should be preparing for a war with China."

The biennial operation - called "Exercise Talisman Sabre" - trains both country's forces in "high-end" war fighting, according to the Department of Defence.

For the first time, Japanese defence force personnel are participating, which some believe could flare up regional tensions.

Professor Richard Tanter, of the Nautilus Institute for Security and Sustainability, said the "war games" exercise, which is being held simultaneously at a site near Darwin, wasn't in Australia's best security interests.

"These war games I think are an unwelcome increase in our integration not only with the United States but with Japan, where Japan has the most nationalist government that country has had since 1945," he said.

Senator Ludlam said such allegiances sent a message to neighbouring countries to "arm up".

"I don't think we should be participating in that kind of provocation," he said.

Activists have already trespassed on the Shoalwater Bay training area as a direct objection to the Australian-US military alliance.

Three Christian activists were arrested at the site on Wednesday and more activists are planning to campaign on the site later this week.

Senator Ludlam backed the activists' actions, despite the risk of them walking into gunfire.

"I think it is dangerous ... you're walking into an area where live firing is under way," he said.

"That's how seriously people take these issues, so good on them."