WASHINGTON (Reuters) - A group of 22 states led by California and five cities are backing the U.S. Environmental Protection Agency's new tailpipe emissions rules after 25 Republican-led states sued last week.

The lawsuit filed Thursday challenges the 2027-2032 model year EPA vehicle emissions rules that aim to cut fleetwide tailpipe emissions for cars and light trucks by nearly 50% over 2026 levels in 2032.

California, New York, Michigan, Pennsylvania and other states sought to intervene in the lawsuit saying they could be harmed if the EPA could not require future reductions in harmful vehicle emissions.

"California won't sit back - we're not going to watch radical Republicans put the profits of big oil over the health of our planet," said Governor Gavin Newsom in a statement.

(Reporting by David Shepardson; Editing by Chizu Nomiyama)