The U.S. Supreme Court sided with the Obama administration on Thursday in rebuffing a bid by 20 states to halt an Environmental Protection Agency rule to curb emissions of mercury and other toxic pollutants from power plants.

The action came about a month after the high court put on hold federal regulations to curb carbon dioxide emissions mainly from coal-fired power plants, the centerpiece of President Barack Obama's strategy to combat climate change.

Chief Justice John Roberts denied a petition made last week by the states, led by Michigan, to put the rule on hold after a federal appeals court decided in December to leave it intact while the EPA reassessed costs of implementing the regulation.