Canada's industrial heartland is joining a group of US states to launch a North American carbon trading market, Ontario Premier Dalton McGuinty announced Friday.

The province is the fourth to join the Western Climate Initiative, which includes also California, Arizona, Montana, New Mexico, Oregon, Utah and Washington.

"We're proud to be welcomed into this important organization of climate change leaders across Canada and the United States," McGuinty said in a statement. "We all have a part to play in the fight against climate change."

The group was established in February 2007 by US state governors frustrated by what they saw as US federal inaction on climate change, to develop regional strategies to address climate change.

McGuinty too has criticized Canada's government for its lackluster plan to stem global warming.

Last year, the Western Climate Initiative set a target to cut greenhouse gas emissions for the region by 15 percent below 2005 levels by 2020.

In August, the partners are expected to announce details of a proposed market-based CO2 cap and trade mechanism to help achieve that reduction goal.