Firefighters in New Mexico have failed to pin back the flames of the United States’ largest wildfire, which is burning perilously close to a string of mountain villages.

The blaze is the most destructive of dozens in the US southwest that are more widespread and burning earlier than normal in the year due to climate change, scientists say.

Thousands of people in the Mora valley, about 60 kilometres northeast of Santa Fe, prepared to leave as smoke billowed from forest around the nearby farming community of Ledoux.

Ember storms

High winds blew embers more than a kilometre, spreading a wildfire that has scorched about 303 square kilometres, of the Sangre de Cristo Mountains since April 6, destroying hundreds of homes and structures.

“It looks very scary out there,” incident commander Carl Schwope told a briefing. “With the rate of spread, it’s very difficult for us to get any fire control.”

Winds were expected to blow from the south on Saturday, pushing the blaze towards villages such as Mora, as well as the city of Las Vegas, with a population of 14,000, fire officials said.

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“It’s coming, and it’s here,” said Mora County sheriff’s official Americk Padilla, urging residents to leave to the towns of Taos and Angel Fire if requested.

More than two decades of extreme drought have turned forested mountains and valleys into a tinderbox, fire expert Stewart Turner said.

“It’s moving a lot faster than we anticipated,” Turner said of the blaze. “This is a very, very serious fire.”

-AAP