Firefighters battling to protect the world's biggest tree from wildfires ravaging the parched United States said Friday they are optimistic it can be saved.

Flames are creeping closer to the majestic General Sherman and other giant sequoias, as man-made climate change worsens California's fearsome fire season.

General Sherman, the world's biggest tree, has been wrapped in foil to protect it from flames
General Sherman, the world's biggest tree, has been wrapped in foil to protect it from flames NATIONAL PARK SERVICE / Handout

"We have hundreds of firefighters there giving it their all, giving extra care," Mark Garrett, communications officer for the region's fire department, told AFP, of the operation in Sequoia National Park.

Crews are battling the spreading Paradise and Colony fires, which have so far consumed 4,600 hectares (11,400 acres) of forest since they were sparked by lightning a week ago.

The fire-proof cladding that firefighters are using is the same material they deploy to protect vulnerable homes
The fire-proof cladding that firefighters are using is the same material they deploy to protect vulnerable homes NATIONAL PARK SERVICE / Handout

The blazes are threatening Giant Forest, a grove of around 2,000 sequoias that includes five of the largest trees on the planet -- some up to 3,000 years old.

The biggest of them all, the General Sherman stands 83 meters (275 feet) tall.

On Thursday, General Sherman was wrapped in fire-proof blankets -- aluminum foil intended to protect its giant trunk from the worst of the flames.

A dead tree (L) stands alongside living trees as smoke rises during the KNP Complex fire in the Sequoia National Forest near Red Fir, California on September 17, 2021
A dead tree (L) stands alongside living trees as smoke rises during the KNP Complex fire in the Sequoia National Forest near Red Fir, California on September 17, 2021 AFP / Patrick T. FALLON

By Friday, managers felt they had the upper hand, thanks in part to clearing of undergrowth and controlled burns that starve the fire of fuel.

"I think the most challenging part is the terrain here," said Garrett.

Photographer Stuart Palley (L) takes photographs of giant sequoia trees among smoke filled skies in the "Lost Grove" along Generals Highway north of Red Fir during a media tour of the KNP Complex fire in the Sequoia National Park in California on Septembe
Photographer Stuart Palley (L) takes photographs of giant sequoia trees among smoke filled skies in the "Lost Grove" along Generals Highway north of Red Fir during a media tour of the KNP Complex fire in the Sequoia National Park in California on September 17, 2021. AFP / Patrick T. FALLON

But "we haven't seen explosive fire behavior; it really slowed down and gave us a chance to get ahead of it."

Around 600 personnel are involved in the fight.

"We have folks up in the Giant Forest protecting structures and preparing everything.

"The fact is that they've been prescribed burning for the past 25 or 30 years so it is really prepared."

Millions of acres of California's forests have burned in this year's ferocious fire season.

Scientists say global warming, stoked by the unchecked use of fossil fuels is making the area ever-more vulnerable to bigger and more destructive wildfires.

The enormous trees of the Giant Forest are a huge tourist draw, with visitors traveling from all over the world to marvel at their imposing height and extraordinary girth.

While not the tallest trees -- California redwoods can grow to more than 300 feet -- the giant sequoias are the largest by volume.

Smaller fires generally do not harm the sequoias, which are protected by a thick bark and often only have branches 100 feet above the ground.

But the larger, hotter blazes that are laying waste to the western United States are dangerous to them because they climb higher up the trunks and into the canopy.