Prime Minister Tony Abbott says there is no time limit on Australia's military deployment to the Middle East to fight Islamic State.

And he has left open the door to six Australian Hornet jets, which are currently bombing Islamic State targets in Iraq, expanding operations into Syria in the future.

Prime Minister Tony Abbott, flanked by Immigration Minister Peter Dutton and Justice Minister Michael Keenan on Wednesday. Credit:Alex Ellinghausen

The comments come after Canadian Prime Minister Stephen Harper announced overnight on Tuesday that his nation's mission in the Middle East would be extended up to 12 months, until March 30, 2016, and that its mandate would be expanded to target Islamic State in Syrian territory, as well as Iraq.

Canada is the second Western nation after the United States to conduct strikes in Syria and like Australia, has six Hornets, a refuelling aircraft, a surveillance aircraft and a small team of special forces.