U.S. President Barack Obama's decision to attend the Copenhagen climate-change conference placed the Harper government on the defensive at a time of rising federal-provincial tensions over environment policy and an internal report that faults federal efforts.

The Prime Minister indicated Wednesday that Canada will be represented at the meeting in the Danish capital by Environment Minister Jim Prentice. The conference will be attended by 65 leaders, including those of the United Kingdom, Germany, France, Spain, Japan, Australia and Brazil. Leaders of China and India, two major emitters, have yet to confirm their attendance.

The U.S. President added his name to the list Wednesday and "put on the table" a commitment to cut emissions by 17 per cent, from 2005 levels, by 2020.

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"I have always been clear, if there is a meeting of all major leaders involving climate change, I will of course attend," Stephen Harper told the House of Commons Wednesday.

The original goal of the Copenhagen conference was to produce a new global climate-change treaty to replace the 1997 Kyoto Protocol. In recent weeks it became clear that delegates were likely to produce, at best, an outline for an agreement to be considered late next year.

Canada, meanwhile, is having internal difficulties with the climate-change file. Individual provinces have broken away from the federal position: Quebec this week unveiled an ambitious plan to reduce greenhouse gases and criticized Ottawa's lack of action. Provincial environment ministers were meeting with Mr. Prentice Wednesday night.

A recent Treasury Board report on the performance of all federal departments has harsh words for Ottawa's efforts. The report, titled Canada's Performance 2008-09: The Government of Canada's Contribution , found a "declining performance" in air quality, biodiversity, and greenhouse gas emissions.

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At the same time, the report says planned spending on grants and contributions to further the Clean Air Agenda during the 2008-09 fiscal year fell nearly $60-million short of target.

Mr. Prentice's office and the Environment department did not respond to questions about the report.

Environmental activists and opposition members said Wednesday that the absence of the Canadian prime minister at the Copenhagen conference would demonstrate a lack of interest.

"This is the most important international negotiation that Stephen Harper will ever be involved in," said John Bennett, the executive director of the Sierra Club of Canada, an environmental group. "To stay away is bordering on criminal."

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Mr. Harper is likely to hear about the need for a more action when he attends the Commonwealth Heads of Government meeting in Trinidad later this week.

Many of the Commonwealth nations are small islands that stand to fare badly if world sea levels rise. If an international agreement on the reduction of greenhouse gases is not reached, many of small island nations will disappear, Albert Binger, a representative of the tiny countries, said Thursday.

Canada may have to make sacrifices to curb emissions, said Mr. Binger. At worst, he said, they will cost Canadians "a few years of economic growth, probably a little higher electricity bills, probably a little higher fuel for your car. For us it's our entire way of life. Now, is that a fair trade?"