U.S. Supreme Court justices have debated putting new limits on the Environmental Protection Agency¡¯s power to tackle greenhouse-gas emissions, as they considered a case that threatens to undercut U.S. President Joe Biden¡¯s climate agenda.

Hearing two hours of arguments in Washington, the justices gave a mixed reception to Republican-led states and coal companies seeking to bar the EPA from issuing a sweeping plan to reduce carbon emissions from power plants. The Biden administration is defending the agency¡¯s authority, with backing from power companies and environmental groups.

Justice Samuel Alito questioned the administration¡¯s assertion that it can broadly push electricity generation away from high-emission sources, as long as it doesn¡¯t impose unreasonable costs or threaten grid reliability.