The Abbott government pushed for Washington to request that Australia expand its air strikes against the Islamic State terror group from Iraq to its more dangerous neighbour Syria, Fairfax Media has learnt.

Tony Abbott confirmed on Tuesday that "some weeks ago" US President Barack Obama had asked him to consider expanding RAAF strikes to Syria.

But senior government sources have told Fairfax Media that the driving force for the formal request received last week from the United States for the RAAF to join the air campaign in Syria came more from Canberra – and in particular the Prime Minister's office – than from Washington.

Visiting remote Indigenous communities in the Northern Territory, Mr Abbott said the government was still considering the request but expected to make a decision within the next week.

"I had a request from President Obama some weeks ago to consider strikes into Syria," Mr Abbott said. "After that, I asked our military officials to talk to the Pentagon and in the wake of those conversations, a formal request for Australian involvement in air strikes in Syria has come. We'll consider this and we'll make a decision in the next week or so."

Mr Abbott and Mr Obama are understood to have discussed the possibility of Australian air strikes in Syria during a telephone call in July initiated by Mr Abbott who had rung his American counterpart to offer sympathies over the Chattanooga shootings.

Government sources say it was Mr Obama who raised Syria as a topic and then made the first suggestion of Australia's expanded role.

But it is widely known in government circles that Mr Abbott has long been keen to do more in the fight against the Islamic State, which has taken swaths of territory stretching across Syria and Iraq and established affiliates in Libya, Egypt and Saudi Arabia.

Fairfax Media asked Defence Minister Kevin Andrews who initiated the discussion about possible Australian air strikes in Syria and whether the US request came without Canberra's prompting.

A spokesman for Mr Andrews said: "As the PM has said today, this was first raised with him by the President of the United States.

"Now that the US Secretary of Defence has asked Australia to consider extending its current counter-Daesh air operations into Syria, the government will consider this request in the normal way, and in close consultation with our coalition partners."

Syria is far more complex than Iraq because there is a full-blown civil war being waged and any diminution of Islamic State's power will benefit the dictator Bashar al-Assad, whose rule the West opposes. Meanwhile, Russia, Turkey and Iran are all pursuing their own interests regarding Syria.

The US, Canada and several Arab countries are already carrying out air strikes against the Islamic State in Syria.

Opposition Leader Bill Shorten said Labor had received an "initial briefing" from the government on Monday but stressed "we're not going to rush into this".

The Chief of Joint Operations for the Australian Defence Force, David Johnston, last week said any Australian involvement would "not be a game changer" in Syria. Australia is currently carrying out regular strikes in Iraq.

Peter Leahy, the former chief of army and now head of Canberra University's National Security Institute, said he had "no objection" to expanding strikes to Syria but said the coalition needed a better plan for Syria and the whole region to defeat extremism.

"We are following the US, which has no clear conception of what victory looks like," he said.

Peter Jennings, executive director of the Australian Strategic Policy Institute, agreed a better overall plan was needed but said extending air strikes into Syria was justified.

"The argument for it is that we'll never defeat IS unless we're able to target their leadership and that means being prepared to engage in more aggressive air strikes against is targets in al-Raqqa," he said.

He said this meant a higher risk to Australian personnel, as the case of the downed Jordanian pilot who was burnt to death in a cage by Islamic State showed in February.

Former top defence bureaucrat Allan Behm said Australia's expanded role into Syria would probably have little impact.

Mr Behm said the US-led air-only campaign was "a sideshow" because at best it could achieve a temporary gain, taking up time before it was realised that the only lasting solution in the war-torn region would be some form of negotiated settlement.

Former Australian Army general John Cantwell, who led Australia's forces in Afghanistan, said it was puzzling why the expansion had been sought, because there were few "viable" military targets.

"More flexibility is good in a general sense, [but] mission focus carries greater weight," he said.

Australia's mission creep

June 2014 Tony Abbott warns that a "terrorist state" could emerge if Islamic State consolidates its recent lightning gains in Iraq from its home base in neighbouring Syria.

August RAAF planes begin air drops of food, water and supplies to minority Yazidis stranded on Mount Sinjar in northern Iraq. Abbott flags possible further involvement.

Early September RAAF planes begin delivering weapons and munitions to Iraqi Kurds. Abbott reveals US has made a "general request" for more military help from Australia.

Mid-September Abbott announces about 600 ADF personnel will be stationed in the Middle East to carry out air strikes and advise the Iraqis on the ground.

Early October First aerial support missions over Iraq. Four days later, bombing runs begin.

November The government begins weighing up sending several hundred additional troops to train Iraqis.

March 2015 Abbott confirms Australia will send 300 troops for training. The first of these are deployed about six weeks later.

June Abbott strongly hints he is looking at ways to contribute further in the fight against Islamic State.

August Abbott confirms Australia has discussed with allies expanding RAAF strikes into Syria and, a week later, confirms a formal request has come from the US.

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