The reelection of President Bush is pushing the Canadian government toward a decision it had hoped to avoid: whether to join a new U.S. system designed to shoot down any missile headed for North America.

Off Canada's northwest shoulder, the United States already is lowering five-story interceptor missiles into silos in Alaska to start the experimental and controversial missile defense system that Bush has championed. His administration has made clear it would like Canada to be part of the project.

But a new opinion poll released this month showed 52 percent of people surveyed were opposed to the plan, and antipathy here to Bush was intensified by the contentious U.S. election. Opposition from Canada's splintered political parties has also given Prime Minister Paul Martin's government, already operating with a minority in the parliament, serious pause about promoting missile defense.

"I think this is one issue they would have liked to have skipped," Gordon O'Connor, a Conservative Party member of parliament, said of Martin's Liberal Party.

Sidestepping the issue will become harder given Bush's expected official visit to Ottawa before his second inauguration in January. Political observers said Bush is unlikely to press Martin for a decision, to avoid being seen as strong-arming Canada. But the missile defense issue has returned to the center of political debate, with supporters arguing that Canada needs to cooperate with Washington to help mend ties strained by the disagreement over the war in Iraq.

"There's an influential community that wants Canada to reassert itself as the United States' best friend, a position we lost to the United Kingdom," said Michael Byers, a security expert at the University of British Columbia in Vancouver. "There's a desire to make up, in effect, for the refusal to go along with the Iraq war."

Proponents of the missile defense plan point to Canada's long partnership with the United States in NORAD -- the North American Aerospace Defense Command. They say Canada must continue to be included in planning by the United States for defense of the continent. And they note that, so far, the Bush administration is asking only for political support, not land or money for the system.

"Do we want the Americans to go ahead with something to defend North America that we're not going to participate in?" Defense Minister Bill Graham, who once opposed the system, argued in a televised interview in September.

Opponents echo the complaints of critics in the United States, arguing that the missile defense system is unproven, technologically difficult, hugely expensive and based on an outdated assumption that an attack will come in the form of an airborne missile. In addition, critics here say the system undermines Canada's preference for multinational teamwork and agreements over weapons and defense machinery.

"There are places we should be cooperating with the United States, but this is way down on the list," said John Polanyi, a chemist and Nobel laureate at the University of Toronto who has joined a phalanx of academics and political figures opposed to the system. He asserted that the missile defense plan inevitably would lead to putting weapons in space, long anathema to Canada.

"I would think that with Canada squawking all the time against weaponization of space, that would make us an unlikely partner for this," Polanyi said. "To be a good ally, you don't pick the weakest ideas of your ally to support, you pick the strong ones. This isn't one."

Martin's government is trying to avoid a clash over the issue that could weaken its already wobbly hold on power. It opposed a demand by the New Democratic Party for a series of public hearings on the subject.

"The majority of Canadians have made it quite clear they do not support Bush's values," said Alexa McDonough, a New Democratic Party parliament member from Halifax, Nova Scotia. "If we really think this is how we are going to build a safer world, we'd have to accept that having nuclear bits flying around above our head is good."

The main opposition group, the Conservative Party, has generally supported joining the project. But in a maneuver employed to make life difficult for Martin, the Conservatives have declared themselves neutral and demanded a parliamentary vote on the issue. The ruling Liberal Party reluctantly agreed, but announced that the result would be "nonbinding," and has yet to schedule the vote.

"If the government doesn't bring it to a vote, the opposition will force it," said Graham, the Conservatives' point man on the issue. "The opposition parties will decide whether it is binding. The government has to be careful. They are a minority."

Some analysts argue the political jockeying is largely irrelevant because the United States could go ahead with the program with or without Canada's participation. Last summer, Canada quietly agreed that the joint U.S.-Canada NORAD operations center in Colorado Springs could share incoming missile information with NORTHCOM, the U.S. command that will control the 40 interceptor rockets planned for Alaska and California and at sea.

"From a technical perspective, Canada is already in," said Byers, the security expert. "It has made the decision to cooperate to the degree necessary to let it go forward."

An interceptor missile, part of the Bush administration's missile defense system, is placed in position in September at Fort Greely, Alaska.Prime Minister Paul Martin is expected to meet with President Bush in the coming weeks.