US states sue Trump over his move to scrap greenhouse gases ruling

Three dozen states and local governments have challenged the Trump administration's reversal of a landmark Obama-era scientific ruling which held that greenhouse gases were a threat to public health.

The lawsuit seeks to overturn the administration's repeal last month of the 2009 "endangerment finding" that underpins all US policies aimed at lowering emissions from cars, power plants and other sources of planet-warming emissions.

Several environmental organisations filed a similar lawsuit last month.

President Donald Trump touted the climate change rollback as a major achievement, calling it a victory over the Democratic Party's "radical" energy and climate policies.

The petition filed in the US Court of Appeals argues that overturning the "endangerment finding" violated provisions in the Clean Air Act.

The group challenging the administration includes 23 states and 17 cities, counties and state agencies, among them New York City, Los Angeles, San Francisco, Boston, Chicago and the Pennsylvania Department of Environmental Protection.

Letitia James, New York State's attorney general, said the Trump administration's decision to throw out the ruling ignored the reality that "the climate crisis is here, and it is already reshaping the way we live".

"Instead of helping Americans face our new reality, the Trump administration has chosen denial, repealing critical protections that are foundational to the federal government's response to climate change," James said in a statement.

The White House did not immediately respond to a request for comment.

The decision to repeal the 2009 ruling represented the latest act in a yearslong effort by Trump - who has often called climate change a "hoax" and "con job" - to undo policies that Democrats and climate experts say are necessary to rein in global warming.

"This radical rule became the legal foundation for the Green New Scam," Trump said while announcing the repeal of the Environmental Protection Agency's ruling.

EPA Administrator Lee Zeldin called the move "the single largest act of deregulation in the history of the United States of America."

Trump's decision drew a sharp rebuke from former President Barack Obama and other Democrats.

"We'll be less safe, less healthy and less able to fight climate change - all so the fossil fuel industry can make even more money," Obama said in a social media post.

Since returning to office the president has withdrawn the US from the Paris climate accord, which he also did in his first term, and rolled back fuel economy standards for cars, among other steps.