Augusta, Maine ? Governors from seven Northeast states said Tuesday they have agreed to the first multistate program in the nation to reduce emissions of carbon dioxide.

The Regional Greenhouse Gas Initiative said the plan would curb carbon dioxide emissions from power plants by 10 percent by 2019. It was signed by governors from Connecticut, Delaware, Maine, New Hampshire, New Jersey, New York and Vermont.

Lawmakers in each state still must approve the plan.

“This historic agreement represents the first significant step toward reducing greenhouse gas emissions in this nation,” Delaware Gov. Ruth Ann Minner said in a statement.

The bipartisan RGGI has been working since 2003 on a plan to cut greenhouse gases that contribute to global warming. Last week, Rhode Island and Massachusetts balked at signing the pact amid concerns about potential economic effects.

The proposal would freeze utility emissions at current levels from 2009 to 2015, and then require a 10 percent reduction by 2019. It also would create a market for greenhouse gases, allowing those who lower emissions to sell excess “credits” to those who can’t cut quickly enough.

Some critics fear the plan could drastically increase electricity rates because it would force companies to build new plants, or convert plants to use natural gas.

According to New York Gov. George E. Pataki’s office, some projections estimate that average household bills could increase by approximately $3 to $21 annually.

“We’re not opponents of the idea, but we can’t support something so poorly designed,” said Anthony Buxton, counsel to the Industrial Energy Consumer Group, representing Maine’s largest consumers of electricity.