Image copyright Reuters Image caption Mr Trudeau and Mr Harper both appeared at campaign events on Friday

Canadian Liberal leader Justin Trudeau has promised that improving relations with the Obama administration will be a top priority if elected prime minster.

He said Canada's ties with its largest trading partner have been frayed by Prime Minister Stephen Harper's hard push for the Keystone pipeline.

Mr Trudeau supports the pipeline, but says he is willing to work with the US to address environmental concerns.

The Liberal Party is leading the polls in the run-up to Monday's election.

"It'll be one of my most crucial priorities to begin once again having a productive and constructive relationship with our closest ally and neighbour," Mr Trudeau said on Friday in Toronto.

The Keystone XL would send more than 800,000 barrels a day of mostly Canadian oil to Nebraska. From there, the oil would travel to refineries and ports along the US gulf coast.

US President Barack Obama vetoed a Republican bill approving the pipeline in February.

Mr Trudeau said he wants to gain common ground with Mr Obama on "more issues than Keystone XL".

Canadian general election 2015

Media playback is unsupported on your device Media caption What's the election about?

Canadian election day is 19 October. Its formal campaign season lasts 78 days.

The Canadian Parliament is comprised of 338 constituencies, called ridings.

Members of parliament are elected in a "first past the post" system where the candidate with the most votes wins.

Canada's prime minister is leader of the party which wins the most seats.

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"That has actually been a point of frustration for the Americans that I've spoken with, that all this government wants to talk about is a single pipeline project," Mr Trudeau said.

Mr Harper, who leads the Conservative Party, and New Democrat Party leader Thomas Mulcair also made campaign stops on Friday.

Media playback is unsupported on your device Media caption Prime Minister Stephen Harper is fighting for a record fourth consecutive term in office

After leading the country for the past 10 years, the prime minister is struggling to stay in power after Canada slipped into recession due to falling oil prices.

Shifting gears from economic issues, Mr Harper is now stressing cultural and social issues on the campaign trail.

He has come out strong against appeals to legalise marijuana and he has opposed a court ruling that allows people to take the oath of citizenship wearing face coverings or niqabs.

All of Mr Harper's opponents agree with the ruling, and some rivals say Mr Harper is using prejudice against Muslim people to gain votes.