UPDATE 1-The U.S. Supreme Court limits federal power to curb carbon emissions.

(Updates with reactions and adds author's signature)

By Lawrence Hurley and Valerie Volcovici

WASHINGTON, Jun 30 (Reuters) - The U.S. Supreme Court on Thursday imposed limits on the federal government's authority to issue far-reaching rules to reduce carbon emissions from power plants, in a ruling that will undermine President Joe Biden's plans to tackle climate change.

The court's six-to-three ruling restricted the Environmental Protection Agency's (EPA) authority to regulate greenhouse gas emissions from existing coal and gas-fired power plants under the landmark Clean Air Anti-Pollution Act. The government is currently working on new regulations.

The court's six conservatives were in the majority in the decision written by Chief Justice John Roberts, with the three liberals dissenting.

"President Biden will not relent in using the authorities he has under the law to protect public health and address the climate change crisis," a White House spokesman said.

The ruling is likely to have implications beyond the EPA, as it raises new legal questions about any major decisions made by federal agencies. The Supreme Court's conservative majority has shown continued skepticism about expanding federal regulatory authority.

The justices reversed a 2021 decision by the U.S. Court of Appeals for the District of Columbia District Court that had struck down former Republican President Donald Trump's Affordable Clean Energy rule.

That rule, which the Biden Administration has said it does not intend to uphold, would impose limits on a provision of the Clean Air Act called Section 111 that gives the EPA authority to regulate emissions from existing power plants.

The ruling was based on what is called the "significant issues" legal doctrine, which requires explicit congressional authorization to act on matters of great importance and societal impact.

In January, the justices adopted that theory when they blocked the Biden administration's "vaccine-or-test" policy for big business, a key element of its plan to combat the COVID-19 pandemic.

The decision will limit the EPA's ability to issue any power plant regulations that would drive an ambitious national shift in energy policy toward renewables.

Roberts wrote that while capping carbon emissions at a level that would force a nationwide energy transition might be a sensible policy solution, "it is not plausible that Congress would give EPA the authority to adopt such a regulatory scheme on its own."

California Gov. Gavin Newsom said the Supreme Court "sided with the fossil fuel industry, amputating the EPA's basic ability to address climate change."

The Biden administration wants the U.S. energy sector to be decarbonized by 2035. The United States, second only to China in greenhouse gas emissions, is a key player in efforts to combat global climate change. (Edited in Spanish by Ricardo Figueroa)