VANCOUVER - A group of Canadian provinces and American states released a blueprint Tuesday for a regional cap-and-trade system to curb greenhouse-gas emissions.

They hope their plan will one day serve as a model for North America, but they have a long way to go.

The Western Climate Initiative -- which includes Ontario, Quebec, B.C. and Manitoba, as well as seven western states -- is the latest collection of regional governments to set up a cap-and-trade scheme that will allow polluters to buy and sell credits to stay within gradually decreasing emissions limits.

Its goal is to reduce greenhouse-gas emissions to 15 per cent below 2005 levels by 2020, a figure that combines the targets already set by each member government.

The program will start small, with just three provinces and two U.S. states prepared to sign on when it comes into effect in 2012.

Of the 11 member jurisdictions in the initiative, only B.C., Ontario, Quebec, California and New Mexico are currently taking steps to join the cap-and-trade system.

But Michael Gibbs of California's Environmental Protection Agency said the climate initiative hopes more provincial and state governments will join, and it wants to eventually link up with two other cap-and-trade systems that are in the works and up and running in the midwestern and eastern United States, respectively.

Ultimately, said Gibbs, the governments behind the plan want Ottawa and Washington to follow their lead.

"We think that we've put forward a strategy that works well, that provides reliable emissions reductions, that is affordable and actually supports economic growth, so we see this as leadership," Gibbs said during a conference call with reporters.

The document released Tuesday includes detailed recommendations for how the cap-and-trade system would work, with each province and state determining its own emissions targets and designing regulations to auction off credits, known as "carbon allowances."

In 2012, the system will include a list of large polluters that emit more than 25,000 tonnes of carbon dioxide per year and will expand in 2015 to include transportation and commercial fuel producers.

In B.C., rather than expanding in 2015, some emitters will remain under the province's carbon tax, while facilities that fall under cap-and-trade will be exempt from the tax.

Polluters will also be allowed to use carbon offsets to control their emissions levels, but there will be a limit on how much a company can rely on offsets to stay within their targets.

Over time, each region's emissions caps will decrease as they approach their 2020 goals.

It's not clear whether the federal governments of either country will create their own cap-and-trade systems any time soon.

In the United States, President Barack Obama's plan to pursue a cap-and-trade system has been stalled in the Senate.

Canada's environment minister, Jim Prentice, has said he's waiting to see what happens in the U.S. before deciding what Canada will do. Prentice's office did not return calls for comment on Tuesday.

Ian Bruce of the David Suzuki Foundation welcomed the Western Climate Initiative's plans.

"It's a major step forward, and shows states and provinces are willing to lead the way to a clean-energy economy in the absence of federal leadership," Bruce said in an interview.

"Their leadership will likely be the blueprint for a national approach."

Bruce said he was concerned about some apparent "loopholes," such as the use of offsets to help polluters stay within their caps, but he said that may still be addressed as the cap-and-trade system is developed.

The plan is facing some resistance south of the border.

The Utah legislature has passed a resolution urging that state's governor to pull out of the initiative.

And in Arizona, Republican Gov. Jan Brewer issued an order earlier this year keeping the state out of the cap-and-trade system. Ben Grumbles of Arizona's environmental agency said the state is worried its economy would suffer.

"Her (Brewer's) message has been, let's work together to green and grow rather than cap and trade the state's economy," Grumbles said in an interview.

"There is a strong difference of opinions, but increasingly the stakeholder groups in Arizona feel that a cap-and-trade program offers more costs than benefits, and could be very complex and uncertain."