Wildfires in the United States burned a record 10.1 million acres (4.1 million hectares) in 2015 and the US government spent $2.6 billion to fight fires, according to the US Agriculture Department.

The area burned last year broke the 2006 record of 9.9 million acres (4 million hectares), the Agriculture Department said on Wednesday.

The 2015 fires destroyed more than 4,500 homes and other structures and killed 13 firefighters, it said.

The Western states of Alaska, California, Oregon and Washington which are facing a historic drought were especially hard hit.

"We take our job to protect the public seriously, and recently, the job has become increasingly difficult due to the effects of climate change, chronic droughts, and a constrained budget environment in Washington," Agriculture Secretary Tom Vilsack said.

The US Forest Service, an agency of the Agriculture Department, spent more than $2.6 billion on firefighting last year.

By 2025, the Forest Service estimates that 67 percent of its budget will be used for fighting fires, an enormous increase from 16 percent in 1995

Firefighting costs reached a record $243 million in a one-week period during the height of fires in August, the statement said.

Agriculture Department officials have warned that fire seasons are starting earlier and lasting longer than years ago.

Scientists say the drought-stricken US West Coast has the potential to strengthen wildfires that could destroy homes, affect watersheds and cost hundreds of millions of dollars to extinguish during the warm summer months.

California’s four-year drought has already cost the state billions of dollars and placed thousands of jobs at risk. More than 12 million trees in California forests have died and more are expected to do so soon, according to a Forest Service report.