The orders would impose new emission limits for automobiles and trucks, toughen energy conservation goals for state agencies and require state-owned vehicles to use alternative fuels such as ethanol and biodiesel.

The rules, which would strengthen existing laws and therefore not need the approval of the legislature, would establish targets for Florida to reduce its greenhouse gas emissions to 2000 levels by 2017, to 1990 levels by 2025 and by 80 percent of 1990 levels by 2050.

The regulations would also set milestones for electric utilities culminating in a reduction in emissions of 20 percent of 1990 levels by 2050. Power companies would also be required to produce at least 20 percent of their electricity from renewable sources, focusing on solar and wind power.

Florida is one of the fastest-growing US states and its estimated population of 18 million ranks behind only California, Texas and New York.

US states have begun passing their own greenhouse-gas regulations because Washington has not passed national laws. President George W. Bush has also rejected the international Kyoto agreement on reducing greenhouse gas emissions.

New Jersey Gov. John Corzine, a Democrat, signed a law last week mandating cuts of greenhouse gas emissions by about 16 percent by 2020 and 80 percent by 2050.

Environmentalists said the New Jersey law was tougher than California's because the 2050 reduction is an enforceable standard, where California's is just a target. The drafts of Crist's orders for Florida also refer to targets.