OTTAWA — Canada’s Prime Minister Stephen Harper said Monday the U.S.-led coalition against the Islamic State was not doing as well as had been hoped in Syria and parts of Iraq.

Harper also said Canada, one of the nations helping Iraq to fight the militant group, would need “a long and sustained strategy” with its international partners against Islamic State, which controls large parts of northern and western Iraq.

Around 70 Canadian special forces troops are working with Kurdish peshmerga fighters in northern Iraq. Six Canadian fighter bombers also are attacking Islamic State positions in Iraq and Syria.

“The intervention has had the effect of largely stopping the advance of ISIS, particularly in the north of Iraq and to some degree in other parts of Iraq and Syria, not maybe as much as we’d liked,” Harper told reporters during an event on Canada’s election campaign.

Polls show Harper’s ruling Conservatives are trailing the left-leaning New Democrats, who have promised to withdraw Canada’s forces from the coalition.

“To protect our country we are going to have to have a long and sustained strategy and work with our international partners and that is what we are doing,” said Harper, who accuses his political rivals of being too soft in the fight against terror.