The federal government will seek Parliament鈥檚 approval to extend and expand Canada鈥檚 mission against Islamic State militants in Iraq, Prime Minister Stephen Harper said Wednesday.

Harper said he will put a motion before MPs when the House returns next week.

鈥淣ext week, it is the government鈥檚 plan to move forward with a request from Parliament for extension and expansion of the mission,鈥 Harper told reporters while making a separate trade announcement in Mississauga, Ont.

Asked whether the mission would be expanded into Syria, Harper said he would 鈥渁ddress those issues鈥 when putting forward his proposal.

鈥淭he current authorization laid open the possibility of going into Syria, though we have not done that,鈥 Harper said.

The mandate for Canada鈥檚 six-month mission to Iraq is set to expire on April 7, and the government had previously indicated that it would seek Parliament鈥檚 approval for an extension.

NDP Leader Thomas Mulcair said the opposition is not surprised by Harper鈥檚 announcement, but is 鈥渧ery shocked鈥 to hear that the prime minister is considering sending Canadian troops to a country run by a 鈥渉orrible dictator,鈥 referring to Syrian President Bashar al-Assad.

鈥淭his is not a coalition that we should be part of,鈥 Mulcair told reporters in Burnaby, B.C. He said the U.S.-led coalition has 鈥渘othing to do鈥 with NATO or the United Nations and Canada has 鈥渁bsolute freedom鈥 to stay out of it.

鈥淚 can guarantee you that we will once again be opposed to any involvement of Canadian troops in what is simply not our war,鈥 he said.

Liberal defence critic Joyce Murray said the party 鈥渃annot speculate鈥 on a proposal that has yet to be presented. Butshe said Islamic State 鈥減oses a real and serious threat to security around the world and in Canada.

鈥淟iberals believe that Canada does have a role to play in the international effort against (ISIS).鈥

Last fall, about 600 Canadian military personnel were committed to join a U.S.-led coalition airstrike mission against Islamic State insurgents. Another 69 Canadian Special Forces are training Kurdish fighters in the north.

Earlier this month, Sgt. Andrew Joseph Doiron was killed in a friendly fire incident when members of the Special Forces were mistakenly fired upon by Kurdish fighters. Three other soldiers were injured.

Afterward, Defence Minister Jason Kenney said Doiron鈥檚 death 鈥渨ill not affect鈥 the government鈥檚 decision to extend the mission.

"We believe that Canada has an important role to play in international security, including the very serious threat of (ISIS), which has explicitly declared war on Canada, (and) encouraged terrorist attacks against Canada civilians," Kenney said at the time.

"There continues to be a very real national security imperative to join with our allies in confronting this organization, and not sitting on the sidelines," he added.

Thomas Juneau, a University of Ottawa professor and Middle East expert, said the first six months of the military mission against ISIS should be considered a success, within reasonable expectations.

鈥淚f anybody expected that Islamic State would be defeated after six months, that was a completely unrealistic expectation and it hasn鈥檛 happened,鈥 he told CTV鈥檚 Power Play Wednesday.

Juneau said ISIS is a 鈥渢ough enemy,鈥 but coalition strikes have weakened the terror group.

He also said that going after ISIS militants in Syria makes sense in his view, but there are many 鈥渓ogistical, security, military and diplomatic challenges鈥 with expanding the mission there.