If the Liberal Party claims victory in the next federal election, Justin Trudeau says, his government would end Canada's bombing mission against ISIS in Iraq and Syria and restore diplomatic relations with Iran, in a dramatic departure from the path taken by the Harper government on foreign policy.

"We'd move away from the CF-18 [bombing] mission," Trudeau said in an interview with Terry Milewski on CBC's Power & Politics. "This government has failed miserably to demonstrate why the best mission for Canada is to participate in a bombing mission," Trudeau said.

And while Trudeau pledged to pull Canadian fighter jets from the Middle East, he doubled down on his commitment to send more military personnel to help train Iraqi security forces — beyond the 70 or so Canadian special operations personnel who are currently embedded with the Kurdish Peshmerga.

"We would engage Canada's military in something we've demonstrated tremendous ability at in Afghanistan and elsewhere: training up local troops doing the fighting on the ground." Trudeau refused to say how many more trainers should be deployed.

U.S. President Barack Obama announced earlier this month that he'd send an additional 450 American troops to advise and assist local Iraqi forces in the fight against ISIS.

Trudeau ruled out committing combat troops to Iraq, even as the security situation there deteriorates. ISIS now controls more than a quarter of Iraq including Mosul, the country's second largest city. ISIS fighters recently took Ramadi, a city about 100 kilometres away from the capital of Baghdad.

"I think 10 years ago we learnt through the first Iraq war what happens when Western troops get involved in combat. They don't necessarily, whether it's Libya, whether it's Iraq, it doesn't lead to the outcomes that people would responsibly like to see," Trudeau said.

Relations with Iran

Trudeau also said he'd move to normalize relations with Iran. The Harper government abruptly closed the Canadian Embassy in Tehran in 2012 and expelled Iranian diplomats from Ottawa.

"I would hope that Canada would be able to reopen its mission, as I understand it, there were security concerns that led to the closing of the mission, but I'm fairly certain that there are ways to re-engage," Trudeau said.

The comments come as negotiators from the so-called P5+1 — the U.S., the U.K., France, China, Russia and Germany — seek to hammer out a deal to limit Iran's nuclear program. Trudeau said he was cautiously optimistic that the two sides could come to an agreement before the June 30 deadline.

The negotiations have faced a barrage of criticism from leaders in Israel, who say any deal with Iran over nuclear weapons is tantamount to appeasement. Israeli Prime Minister Benjamin Netanyahu has said the Iranian regime cannot be trusted and economically punishing sanctions against Iran must be preserved.

No GST hike

The Liberal Party leader also ruled out any new taxes on the middle class to fund any new government initiatives — including a hike to the GST. "Middle-class Canadians have struggled enough — we're not going to be raising taxes for them," Trudeau said.

The Liberals say they will boost benefits to Canadians with children if they're elected. Under the Trudeau plan, families with children under 18 and an annual income below $150,000, about 90 per cent of families, would receive more than they do under the current universal child care benefit.

But the Liberal plan would cost $2 billion more than what the Harper government has set aside for child benefits. Trudeau said he could fill that gap by using the $1.7-billion surplus the federal government is expected to post next year and by putting an end to partisan government advertising.