A coalition of 23 US states and local governments has vowed to challenge in court President Trump's latest Executive Order reversing a raft of President Obama's climate change regulations.
The coalition includes states such as California, Massachusetts and Virginia, as well as cities including Chicago, Philadelphia and Boulder, Colorado.
It will be backed by environmental groups, which have called Mr Trump's Energy Independence Executive Order a threat to public health that goes against the global trend toward cleaner energy technologies.
The order's main target is former president Barack Obama's Clean Power Plan, which required states to slash carbon emissions from power plants - a key factor in the United States' ability to meet its commitments under the Paris climate change accord reached by nearly 200 countries in 2015.
Christiana Figueres, the senior UN official who helped broker the Paris accord, lamented Mr Trump's executive order.
She said: "Trying to make fossil fuels remain competitive in the face of a booming clean renewable power sector, with the clean air and plentiful jobs it continues to generate, is going against the flow of economics."
Mr Trump’s order also asks federal agencies to discount the cost of carbon in policy decisions and the weight of climate change considerations in infrastructure permitting, and it reverses rules limiting methane leakage from oil and gas facilities.