"We do have a made in Canada plan to resolve the problem of pollution and also greenhouse gases," Harper told reporters in Montreal.

"But in order to resolve these issues, in this continent and within our economy, we have to have the participation of the United States. Otherwise, really, there won't be much impact from our efforts."

The comments come after 90 top Canadian scientists pressed Harper this week to develop a national strategy to reduce air pollution soon or risk devastating consequences for Canada's ecosystems, economy and society.

Last year, Canada was flagged in a UN report on global warming as high on a list of countries most likely to run into difficulty implementing Kyoto commitments.

In 2003, Canada had increased its emissions by 24.2 percent from the base 1990 level, far from its 2012 target of a six percent reduction, according to the report published in November 2005.

"I have said all along that Canada would not achieve the Kyoto targets. Canada could not achieve them, and that's just the reality, but we do want to make progress," Harper said on Wednesday.

Harper noted that he and US President George W. Bush talked about climate change at a recent leaders summit in Mexico and that Bush is "discussing an arrangement with other major countries", but offered no details of the plan.

Such a deal would not necessarily be exclusive, he added. Other unspecified options remain too.

"I think you have to try and achieve success at the international level, at the continental level and also at the national level. And our government is looking at all the options," Harper said.

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