Four-star general and former CIA director David Petraeus has urged Australia to join United States airstrikes against Islamic State terrorists in Syria.

On Wednesday evening, Mr Petraeus used his Lowy Institute lecture in Sydney to back the pending request from the US.

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“Taking such an action will do damage do ISIS,” he said.

“There’s a reason why the coalition countries and the US have taken that action and I think that is one that ultimately would be one that Australia should consider.”

The Abbott government is yet to formally respond to the formal request, although senior cabinet ministers have lent their support.

Earlier this week, Foreign Minister Julie Bishop told European nations to join the air strikes — a possible indication of what the government will decide.