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.