BOSTON (AP) -- The Patrick administration has issued final amendments to a regulation it says will reduce up to 90 million tons of carbon dioxide pollution from power plants across nine New England and mid-Atlantic states during the next six years.

Massachusetts and the eight other states that also adopted revisions — Connecticut, Delaware, Maine, Maryland, New Hampshire, New York, Rhode Island and Vermont — are part of the nation's first multi-state "cap-and-trade" program known as the Regional Greenhouse Gas Initiative.

Power plants in the states must buy "allowances" allowing them to emit carbon dioxide. The states auction these allowances.

The revisions to the greenhouse gas initiative standards will lower the existing cap on power plant emissions in the states from the current 165 million tons per year to 91 million tons per year starting in 2014, with additional cuts after that.

By 2020 power plant emissions from the nine states will be half of what it was when the program started in 2005.

The lower cap is also expected to generate about $350 million in additional revenue for Massachusetts by 2020.

Administration officials say the revenues will be used to improve energy efficiency in cities and towns, businesses and homes, which will ultimately reduce energy costs and lower carbon dioxide emissions even more.

The nine states have also called upon the U.S. Environmental Protection Agency to embrace regional cap-and-trade programs when it issues federal rules to cut carbon emissions from power plants.