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The leader of Canada's front-running Conservative Party said Thursday he would stand up to the White House on matters of national interest, but do so without insulting "our biggest customer."

Stephen Harper, whose party is poised to end 13 years of Liberal Party rule when Canadians go to the polls in three days, said the Conservatives would strive to improve relations with Canada's "closest ally" if they win Monday's national vote.

Prime Minister Paul Martin has warned traditionally liberal Canadians that Harper poses as a moderate but supports the U.S. effort in Iraq, opposes abortion and would overturn laws approving gay marriage.

The U.S. and Canada comprise one of the world's largest economic blocs, with $1.5 billion in daily trade, but relations have grown frosty in the last year.

Canada's current Liberal government opposes the war in Iraq and Martin infuriated the Bush administration by opting out of its proposed continental anti-ballistic missile shield. Ottawa routinely rebukes Washington over its lumber tariffs and refusal to join the Kyoto Protocol to reduce greenhouse gases.

Harper's Conservatives have held a solid lead over the Liberals in the polls in the last campaign stretch before Canadians elect a new leader and the 308-seat House of Commons.

"I think that we should obviously have good relations whenever possible with our closest ally and our biggest customer," Harper said Thursday. "I would hope to talk to the president very closely to start us on that track. But that's not going to take us off fighting on specific Canadian interests."

Canada insists the U.S. is violating the North American Free Trade Agreement (NAFTA) by imposing stiff penalties on Canadian lumber.

Canadians typically love it when their leaders stand up to the U.S., but many have grown weary of the verbal sparring.

"I think people are angry, they're fed up," said Steve Belitzky, 60, a Montreal businessman who plans to vote Conservative for the first time.

On Thursday, Martin painted his Conservative rivals as "extreme" right-wingers and said Harper intended to stack the Supreme Court with conservative judges.

"This is no abstract issue; we have a vacancy to be filled on the Supreme Court bench," Martin said. "Never have we seen a major political party with such a conservative agenda as this one — an agenda really drawn from the extreme right in the United States."

Martin insists Harper supports the war in Iraq, which most Canadians disdain. Harper has said Ottawa was right not to send troops to Iraq, but should have publicly offered Washington its moral support in the war.

Harper said Thursday he wants to elevate Canada's military capacity, another demand from the U.S. and NATO allies, who grumble that Canada spends too little on defense.

"The biggest thing I want to do on foreign policy is to increase Canada's foreign policy capacities, whether they be in foreign aid, or military capacity or disaster assistance," Harper said. "We want Canada to be able to do more."

Martin last year pledged more than $10.9 billion to beef up the Canadian military; Harper has pledged an additional $5 billion over the next five years.

Martin insisted Thursday the race was not over and he predicted that progressive voters would flock to the polls to keep the Conservatives out of power.

"We are on the march," he said. "And we are marching toward a remarkable comeback."