TORONTO (Reuters) - Incoming Canadian Prime Minister Justin Trudeau will move quickly to implement campaign promises such as overhauling security legislation, sources in his party say, but faces early challenges with pledges on Syrian refugees and climate change.

Canada's Prime Minister designate Justin Trudeau arrives at a funeral for Former Canadian ambassador Ken Taylor, in Toronto, October 27, 2015. Former Canadian ambassador Ken Taylor, whose role in rescuing U.S. diplomats in a covert operation in 1979 during the Iran hostage crisis was featured in the movie "Argo", died on Thursday, his son told CBC television. He was 81. REUTERS/Mark Blinch - RTX1TIDP

The Liberal leader, who is expected to enjoy an extended honeymoon after his massive Oct. 19 election win ended a decade of Conservative governing, plans to call Parliament to return in early December, the sources said, to start work on an agenda which will also include middle-class tax cuts.

“All the low-hanging fruit, all the ones that he can make a decision on right away, I’m expecting we’ll see a lot of that happening,” said one Liberal Party source, who declined to speak on the record because of the sensitivity of strategic plans.

A second party source, who also spoke off the record, said other measures the Liberals would quickly act on include reinstating a mandatory long-form national census that was canceled by the Conservatives, and naming a commissioner to head an inquiry into missing and murdered indigenous women.

“His instinct to try to tick off as many promises as he can is the right thing to do,” former Liberal Deputy Prime Minister John Manley said in an interview.

Trudeau pledged during the campaign that his first piece of legislation would enact tax cuts for income from C$44,700 ($34,140) to C$89,401 and tax hikes for incomes above C$200,000.

He also promised to repeal controversial elements of Conservative anti-terrorism legislation to give more weight to civil rights.

Moving quickly on easily fulfilled promises will give the Liberals time to work out how to deliver on pledges for major infrastructure spending and legalizing marijuana, which the second Liberal source said was likely to occur towards the end of the Liberals’ four-year mandate.

A Trudeau spokeswoman did not respond to requests for comment.

Trudeau, the 43-year-old son of former Prime Minister Pierre Trudeau, should have little trouble moving his legislative agenda through Canada’s Parliament after his party won 184 of the 338 seats in the House of Commons.

And even the Conservatives of outgoing Prime Minister Stephen Harper, on the hunt for a new leader after being pushed to opposition, predict Trudeau will enjoy plenty of good will.

“There are already some signs of the honeymoon that will go forward,” said Peter Kent, a former Conservative minister reelected as a member of Parliament.

But members of the outgoing government warn Trudeau will have a hard time meeting a promise to bring in 25,000 Syrian refugees by year-end.

By comparison, the United States, with nine times as many people as Canada, is aiming to take in at least 10,000 Syrian refugees over the next year.

“He’s got to make sure that none of those 25,000 refugees are going to cause him any kind of security heartburn,” said Ian Brodie, Harper’s first chief of staff.

A person with direct knowledge of the file, who spoke on condition of anonymity because of the sensitivity of the issue, said officials at the immigration ministry had concluded that the only way to achieve the goal would be to airlift the refugees into Canada and then carry out mandatory health and security checks.

The source said the challenge with screening on Canadian soil is that even if some are rejected, it is hard to deport people once they are in the country.

Outgoing senior Conservative cabinet minister Tony Clement said the Trudeau pledge to bring them all in by year end was unrealistic.

“There’s no way to do that without incurring a lot of expense or alternatively having an impact on our safety and security, he said.

The second Liberal source conceded Trudeau might have to push back the Dec. 31 deadline, but would still bring in 25,000.

“If he has to say he’ll take an extra two or three months to make it happen, I don’t think anyone will think that’s unreasonable,” said the source.

Another early challenge for Trudeau will be crafting a national consensus on climate change, a sensitive topic because of climbing carbon emissions driven by oil production in Canada’s west.

Trudeau has promised to take the 10 provincial premiers, who have wide-ranging control over their natural resources, with him to this year’s U.N. climate change conference in Paris and says he will sit down with them within three months to set a national target.

But already, the right-leaning premier of Saskatchewan, the second-largest oil-producing province, said he was going to Paris to make sure Trudeau didn’t “kneecap our economy.”

One of the Liberal sources said Trudeau would attend the start of the talks on Nov. 30 but was unlikely to stay beyond Dec. 2 so he could return to prepare for the opening of Parliament.

A diplomatic source familiar with the file corroborated this account, saying Trudeau would not spend more than three days in Paris.

($1 = 1.3093 Canadian dollars)