President Joe Biden has approved a disaster declaration that brings new financial resources to stretches of New Mexico devastated by fire since early April.

It comes as firefighters slowed the advance of the largest wildfire in the US as heavy winds relented.

State politician Teresa Leger Fernandez announced the presidential disaster declaration during an evening briefing by the US Forest Service on efforts to contain the sprawling wildfire in north-eastern New Mexico.

It has fanned out across 258 square miles of high alpine forest and grasslands at the southern tip of the Rocky Mountains.

“It will help us do that rebuilding and it will help us with the expenses and the hardship that people are facing right now,” she said.

“We’re glad it happened this quickly.”

Fire chiefs are seizing on an interlude of relatively calm and cool weather to prevent the fire from pushing any closer to the small New Mexico city of Las Vegas and other villages scattered along the fire’s shifting fronts.

Planes and helicopters dropped slurries of red fire retardant from the sky as ground crews cleared timber and brush to starve the fire along crucial fronts.

Bulldozers for days scraped fire lines on the outskirts of Las Vegas, which has a population of 13,000, while crews have conducted controlled burning to clear adjacent vegetation to prevent it from igniting.

Aircraft dropped more fire retardant as a second line of defence along a ridge just west of Las Vegas in preparation for intense winds expected over the weekend.

Strong winds with gusts up to 45mph are expected to return on Saturday afternoon along with above-normal temperatures and “abysmally low” humidity that make for extreme fire danger, said Todd Shoemake, a National Weather Service meteorologist in Albuquerque.

“Sunday and Monday are probably looking to be even worse.”

Nearly 1,300 firefighters and other personnel were assigned to the fire.

Mandatory evacuation orders have been issued for an estimated 15,500 homes in outlying areas and in the valleys of the Sangre de Cristo Mountains that border Las Vegas.

The number of homes destroyed by the fire stands around 170 but could grow higher because officials have not been able to conduct assessment in all of the burn zones.

Mr Biden’s disaster declaration releases emergency funds to recovery efforts in three counties in north-eastern New Mexico where fires are still raging and for southern New Mexico areas where wind-driven blazes killed two people and destroyed more than 200 homes in mid-April.

The aid includes grants for temporary housing and home repairs, low-cost loans to cover uninsured property losses and other relief programmes for people and businesses, a White House statement said.

Emergency service officials acknowledged the physical and emotion toll of the prolonged evacuations.

Las Vegas Police chief Antonio Salazar said his officers would provide “burglary patrols” for evacuated areas and help to maintain order at a local Walmart as people queue to buy supplies.

“Repopulation, that’s one thing we’re very interested in,” San Miguel County sheriff Chris Lopez said. “Everybody wants to get back home.”

Dan Pearson, a fire behaviour specialist with the federal government, said weather forecasters predict two days of relatively light winds before the return of strong spring gales.

“Our prayers are working because we’ve had advantageous winds throughout the fire area today,” he said.

“We’ll take advantage of this fact over the next few days. … What we can do is build resilient pockets.”

The fire was contained across just 20% of its perimeter.

Its flames were about a mile away from Las Vegas, where schools were closed as residents braced for possible evacuation.

Officials at the Los Alamos National Laboratory were warily tracking another wildfire that crept within about five miles of facilities at the US nuclear research complex.

Fire crews worked to widen a road that stands between the fire and Los Alamos while clearing out underbrush and treating the area with fire retardant.

Wildfires have become a year-round threat in the drought-stricken west — moving faster and burning hotter than ever due to climate change, scientists and fire experts have said.

Fire officials also point to overgrown areas where vegetation can worsen wildfire conditions.