Joining a burgeoning movement to address global warming, Gov. Rod Blagojevich on Thursday will order state government to cut its greenhouse gas emissions by the end of the decade.

The election-year plan will require state vehicles and buildings to be cleaner and more energy efficient. But critics noted that unlike a new California law, the initiative fails to impose restrictions on private vehicles and coal-fired power plants, the largest sources of heat-trapping carbon dioxide.

If Illinois fails to cut emissions by 6 percent by 2010, taxpayers will make up the difference by purchasing credits from the Chicago Climate Exchange, a voluntary market where corporations and governments trade the right to emit greenhouse gases.

Blagojevich's top aides said the state is attempting to lead by example. The governor also is creating a panel of experts who will recommend ways to reduce greenhouse-gas emissions from larger polluters, though it is far from certain whether the result will be anything like California's ambitious effort.

"We realize this is not a substitute for a broader policy," said Steve Frenkel, Blagojevich's director of policy development. "But absent any federal leadership on this issue, states are taking the initiative."

Illinois is one of the nation's leading sources of carbon dioxide. The state's coal-fired power plants churned more than 105 million tons of the gas into the atmosphere last year, according to federal records. Only five other states released more.

Although Blagojevich has vowed to make Illinois a leading developer of clean-energy sources, the Democratic governor's administration has approved three new coal plants that would emit about 18 million tons of carbon dioxide a year.

By contrast, state vehicles and buildings are responsible for about 1 million tons of climate-changing gases every year, according to government estimates.

Reducing those emissions by 6 percent--or 60,000 tons--would be the equivalent of taking about 13,000 cars off the road.

To meet that goal, Frenkel said, the state plans to buy more cars and trucks that can run on a high blend of ethanol, the corn-based fuel that produces slightly less carbon dioxide than gasoline. The state currently owns about 2,000 flex-fuel vehicles, or 16 percent of its fleet.

Moreover, wind power and other renewable energy sources are expected to provide 5 percent of the electricity for state buildings by 2010, a change that will reduce the need for fossil fuels.

By joining the Chicago Climate Exchange, the state will be required to reduce emissions or pay for greenhouse-gas credits, which have doubled in price during the last year and currently are selling for about $5 a ton.

The exchange is a voluntary carbon-trading program created by corporations that have agreed to reduce emissions or pay for the right to keep polluting. It is patterned after the U.S. Environmental Protection Agency's Acid Rain Program, which in the last decade has reduced sulfur dioxide emissions from coal-fired power plants.

The EPA program sets an annual national cap on emissions, gives each polluter a certain number of pollution credits (each equal to a ton of sulfur dioxide) and allows utilities to decide how to meet the target. Some installed pollution scrubbers or switched to low-sulfur coal. Others decided to buy more credits.

Since the climate exchange opened in December 2003, more than 200 companies have signed up, including Motorola, IBM, Ford and DuPont. Illinois is joining New Mexico and Chicago among the handful of participating governments.

There is no legal requirement for U.S. companies to address global warming. President Bush promised during his 2000 campaign to reduce carbon-dioxide emissions, but once in office he said it would damage the economy.

A growing number of scientists, though, say the only way to reduce global warming is to dramatically cut greenhouse-gas emissions. The climate exchange is seen as an example of how a mandatory trading system could work.

Among the states, California has taken the most aggressive approach by requiring a 25 percent reduction in statewide emissions by 2020. Governors in seven northeastern states, meanwhile, are developing their own trading programs to reduce carbon dioxide emissions from power plants.

New Mexico's state government has reduced its emissions by 2,000 tons since 2003. But it missed the climate exchange's target and must spend about $50,000 this year on credits to make up the difference.

"We still have a long way to go, but this is a good place to start and it holds people accountable," said Ron Curry, the state's environment secretary.

A campaign spokesman for Illinois Treasurer Judy Baar Topinka, Blagojevich's Republican opponent in the Nov. 7 election, called the state's plan a "sensible idea" but questioned the governor's timing.

Environmental groups had mixed reactions. Some applauded Blagojevich for prompting a statewide debate, while others said his plan doesn't go far enough.

"It's a start, but it's really not moving the ball very far," said Dale Bryk, a senior attorney for the Natural Resources Defense Council. "We would rather see states adopting policies that deal with the major sources of emissions within their jurisdictions."