Prime Minister Tony Abbott says the government expects to make a decision next week on whether to join air strikes in Syria as he brushed aside questions on whether his office pushed for a request from Washington to expand Australia's involvement.

Mr Abbott told reporters  on Wednesday that cabinet's National Security Committee would most likely meet next week to determine whether air strikes against Islamic State in Iraq should be expanded into its more dangerous neighbour Syria.

The committee has to meet to make a decision and it is expected that meeting will occur on September 1.

Mr Abbott said the formal request for increased involvement by Australia had been made in a phone call to him from US President Barack Obama.

But he did not deny reports by Fairfax Media that the driving force for the request came from the government and, in particular, Mr Abbott's office.

"Well, all I know is that I was on the other end of the phone line, the President was on Air Force One, the President had initiated this phone call to talk about the Trans-Pacific Partnership," Mr Abbott told reporters in Bamaga in Cape York.

"After I initially expressed my condolences for the terrorist shootings in Chattanooga (in Tennessee) the President then raised with me the Syrian situation and said that he would be very glad if Australia would do more, including air strikes.

"I was happy to consider that request and our officials would talk and now this request has come from the Pentagon."

Mr Abbott said while Australia's initial commitment was for air strikes in Iraq, it was important Australia did what it could to assist allies in the Middle East and other countries to defeat Islamic State.

"I've long thought that while the legalities are different, the moralities of this issue are the same on either side of the border," he said.

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