Canadian Prime Minister Stephen Harper is standing firm in his belief that the U.S. will eventually approve the construction of the Keystone XL pipeline.

The incumbent Conservative leader, who has faced criticism that his environmental record has hindered approval of the project, defended his handling of the file and his relationship with U.S. President Barack Obama in an election debate Monday in Toronto.

“Barack Obama and I have discussed this particular matter,” Harper said. “He said to me there is nothing he’s asking Canada to do. He’s going to make that decision based on his own assessment of American interest."

TransCanada Corp.’s pipeline linking Alberta’s oil fields to U.S. refineries on the Gulf of Mexico has become a potent symbol in environmentalists’ fight against fossil fuels. It also has become a proxy for a U.S.-Canada relationship that’s grown tense.

The project continues to have “overwhelming public support,” Harper said.

His two main rivals -- New Democratic Party Leader Tom Mulcair and Justin Trudeau of the Liberals -- accused him of fumbling the Keystone file and of degrading ties between the countries. Harper replied that he has a “great relationship with the U.S. administration” and repeated his belief Keystone will ultimately be built.

“When the logic of something is overwhelming in an environmental, economic and energy security sense, its adoption is inevitable,” he said.

Harper’s Conservatives are locked in a narrow three-way race between the Liberals, who favor Keystone, and the left-leaning NDP, which opposes it in part because it would export raw, unrefined oil-sands bitumen.

The debate was the fourth of five in the election campaign, with the final session to be held Friday in Montreal. Canadians go to the polls Oct. 19.

Before it's here, it's on the Bloomberg Terminal. LEARN MORE