Australian lives will be on the line and the government must avoid "mission creep" if it sends military resources into conflict with Islamic State, former chief of Army Peter Leahy has warned.
Toughening language from Foreign Affairs Minister Julie Bishop, who spent Thursday and Friday in meetings with allies at the biennial NATO summit in Wales, has prompted a cautious response from Mr Leahy, who is the director of the National Security Institute at the University of Canberra.
"This is a regional problem with global implications," Mr Leahy said.
"It's time that states like Saudi Arabia, Jordan and Turkey and other regional powers stood up to the problem themselves."
Ms Bishop told reporters that Australia was ready to join a US coalition on Iraq.
"The US air strikes have had some significant impact but there is more that needs to be done to ensure that ISIL doesn't continue to grow and spread its poison beyond the region," she said.
"We talked about a range of ways that the countries can assist a US-co-ordinated approach."
Ms Bishop said Australia would respond when a formal request was made.
"The red line is combat troops on the ground," she said.
"There is no interest from any country present to commit combat troops, but there is much that can be done to seek to combat ISIL in other ways and Australia is prepared to play its part."
No formal request had come yet, Ms Bishop said, so Australia had not committed to joining the action.
"We would weigh the options. We would weigh the risks," she said.
"There must be a clear and proportionate role for Australia. There would have to be a humanitarian objective and there would have to be a realistic assessment of what resources and assets would be required and in what timeframe."
Mr Leahy said the government would need to clearly define its mission.
"Becoming involved in Iraq again is a big step and the big question is: what do we want to achieve there?" he said.
"It's a strategic issue and it will require debate and discussion here and across the globe.
"We must involve Middle Eastern states in any solution. In terms of the limits of our involvement, the government must have a clear view of the strategy and what our mission might involve.
"We must resist mission creep - which is where things happen and we react to that. There must be clear perimeters around what we are prepared to do."
Mr Leahy said he agreed with US President Obama's assessment that IS had to be destroyed.
"I think President Obama is correct," he said.
"But it will not be achieved by air power only - there needs to be diplomatic and other elements of power involved, and we have learned over the past decade or so you cannot control the ground from the air."
Mr Leahy said any military action, even without ground forces, could cost Australian lives.
"We are putting our amed forces in harm's way again and we must be prepared to understand the consequent costs of people being killed or injured," he said.
"The mission again must be clearly articulated and a narrative developed so the Australian public clearly understand why we need to do this."
Hugh White, professor of strategic studies in the Strategic and Defence Studies Centre at the ANU, said during the week, ahead of Ms Bishop's comments, that only those willing to commit huge ground forces would have any hope of being able to shape the outcome.
"The terrorist threat posed by Islamic State to Western countries such as Australia is best met not by military interventions of the kind that have already been tried and have failed in Iraq and Afghanistan, but by the less spectacular but more effective work of intelligence agencies and police forces," he said.