OTTAWA -- Justin Trudeau made a triumphant return to the nation's capital Tuesday and immediately began setting a new tone for the Canadian government, both at home and abroad.

To those around the world who may have had difficulty recognizing the Canada of old during a decade of combative, militaristic Conservative rule under Stephen Harper, the Liberal prime minister-designate had a direct message.

"Many of you have worried that Canada has lost its compassionate and constructive voice in the world over the past 10 years," Trudeau told a boisterous partisan rally in Ottawa.

"Well, I have a simple message for you. On behalf of 35 million Canadians, we're back."

At a news conference later, he also had a reassuring message for civil servants, many of whom complained of being muzzled and ignored by the Harper regime. Trudeau promised to run "a government that listens to, works with and respects the public service."

And he had another message for the parliamentary press gallery, which has been shunned and vilified by the Harper Conservatives, that he intends to run a more open, media-friendly shop.

Fresh from his stunning victory in Monday's election, Trudeau held a formal news conference in the national press theatre -- something Harper did only handful of times and not at all since late 2008. Trudeau said "it's important to underline the important role that the media fills in public discourse and public life" and, when the news conference was over, he vowed: "I'll be back. I promise."

For now, though, tone is all Trudeau can set. He will not officially take office until Nov. 4, when he plans to swear in a new cabinet.

He would not commit to recalling Parliament before Christmas, only to doing so "as quickly as is reasonable."

His schedule for the next two months is anything but reasonable, with four back-to-back international summits scheduled starting in mid-November. Trudeau suggested he may not attend all of them.

He said he's "committed" to attending the United Nations climate change conference with the premiers in Paris at the end of November. That leaves the Liberals just weeks to come up with a national position based on the party's promise to join with the provinces and territories to put a price on carbon and reduce carbon pollution.

As for the G20 summit in Turkey and a meeting of leaders of Pacific Rim countries in the Philippines, Trudeau said only that he hopes to attend. He did not mention the Commonwealth heads of government meeting in Malta, saying he'd have to see how many international trips he can squeeze in while trying to get his new government up and running at the same time.

Nevertheless, Trudeau is already getting a quick introduction to international affairs, fielding congratulatory phone calls from U.S. President Barack Obama, as well as the leaders of the United Kingdom, France, Mexico and Italy.

While he and Obama had a "warm conversation" in which the president teased him about his lack of gray hair, Trudeau said they also discussed his commitment to withdraw Canadian fighter jets from the U.S.-led aerial bombing mission against Islamic radicals in Syria and Iraq. Trudeau believes Canada's military involvement should be restricted to training missions only.

"We talked about Canada's continued engagement as a strong member of the coalition against ISIL. And I committed that we would continue to engage in a responsible way," Trudeau said.

"But he understands the commitments I've made around ending the combat missions."

At the rally earlier, Trudeau used the occasion to thank staff in party headquarters and the 80,000 volunteers whom he credited with making nearly 12 million phone calls and door knocks over the course of the longest campaign in modern Canadian history. But as gruelling as the campaign was, he acknowledged the hard part starts now.

"This afternoon we can celebrate, but our hard work is only beginning."

Both at home and abroad, Trudeau faces several pressing priorities and a raft of longer-term promises.

On the horizon domestically loom key promises from his party's successful campaign: lower taxes for the middle class, the legalization of marijuana, and a slate of democratic reforms including a new electoral system to replace the venerable first-past-the-post regime under which he won a majority of the seats with just under 40 per cent of the vote.

He will also have to move quickly to institute the reforms he's promised to the disgraced Senate, where the Conservatives still hold sway and could prove a roadblock to Liberal legislation. Tory dominance of the chamber could be instantly diluted by filling the 22 vacancies left by Harper.

Trudeau has kicked senators out of the Liberal caucus and has vowed to create a blue chip advisory body to recommend non-partisan Senate nominees in future, a move designed to return the institution to its intended role as an independent chamber of sober second thought.

Trudeau has said the first piece of legislation his government would put forward is one to lower taxes for the middle class and raise taxes for the wealthiest Canadians.

A Liberal government is also committed to revamping the recently enacted omnibus security bill, known as C-51, that gave Canada's spy agency substantial new powers and angered civil libertarians.

Trudeau has also promised the largest new infrastructure investment in Canadian history. The plan would nearly double federal spending on public transit, affordable housing, recreational facilities and other items to almost $125 billion over the next decade.