MONTREAL, September 14, 2009 (AFP) - Environmental group Greenpeace on Monday accused Canada of contributing to a "global climate crisis" by seeking to expand extraction of oil from tar sands in Alberta province.

In a report entitled "Dirty Oil" the organization also says that Canada, along with Japan, is seeking to block progress towards a new global climate change agreement to be finalized at a December summit in Copenhagen.

Greenpeace published its new report shortly ahead of a meeting between Canadian Prime Minister Stephen Harper and US President Barack Obama on Wednesday.

Canada is the biggest supplier of oil for the United States, and the two leaders are expected to discuss expanded extraction from the tar sands.

Greenpeace's report accuses Canada of being a "global carbon bully," working to undermine the emissions goals set by the Kyoto climate change treaty and engaging in "outspoken, aggressive" lobbying to obstruct agreement on new greenhouse gas limits to be negotiated at the Copenhagen summit.

The organization commissioned the report from journalist Andrew Nikiforuk, an expert on tar sands.

"The analysis connects the dots and shows how the tar sands are at the leading edge of climate destruction," said Mike Hudema, a Greenpeace climate and energy campaigner, in a press release.

The extraction of oil from tar sands is much more energy-intensive than other oil extraction operations, Greenpeace said, meaning that "the tar sands have a higher carbon footprint than any other commercial oil product on the planet."

"Some products are now 10 times dirtier than production of oil in the North Sea," the report said.

Since Obama took office, Canadian environmentalists have looked to him to slow the development of oil extraction from the tar fields and break with the policy of his predecessor George W. Bush.