After coming in $400 million over budget following last year's busy fire season, the Forest Service is altering its approach and may let more fires burn instead of attacking every one.

The move, quietly made in a letter late last month by Forest Service Chief Tom Tidwell, brings the agency more in line with the National Parks Service and back to what it had done until last year. It also answers critics who said the agency wasted money and endangered firefighters by battling fires in remote areas that posed little or no danger to property or critical habitat.

Tidwell played down the change, saying it's simply an "evolution of the science and the expertise" that has led to more emphasis on pre-fire planning and managed burns, which involve purposely setting fires to eliminate dead trees and other fuels that could help a wildfire quickly spread.

"We have to be able to structure (fire management) this way to help all of us," Tidwell told The Associated Press. "So that we're thinking about the right things when we make these decisions."

The more aggressive approach instituted last year was prompted by fears that fires left unchecked would quickly devour large swaths of the drought-stricken West, Tidwell said. New Mexico and Colorado reported record fire seasons in 2012, and with dry conditions remaining in much of the region 2013 could be another bad year in the West.

In all, the agency oversees about 193 million acres in 43 states.

But the "kill all fires" approach angered watchdog groups and environmentalists, who said it was expensive and ignored fire's natural ability to rid the landscape of dangerous fuels and bolster forest ecology.

"This new policy gives a lot more flexibility. It takes the blanket policy where every fire was treated the same and gives fire managers more options," said Timothy Ingalsbee, executive director of Firefighters United for Safety, Ethics and Ecology.

"Chief Tidwell's move should restore the confidence of the fire management community that all the training and technology that's been invested to give fire crews the ability to work with fire to restore ecosystems will not be wasted by a return to yesteryear's all-out war on wildfires."

While all federal agencies operate from the same federal wildfire management policy, each has its own goals and ways of interpreting it. The National Parks Service, for example, allows more fires to burn on its lands.

But letting fires burn also has its dangers, even in remote areas.

Last year, the Parks Service allowed a fire to burn that started as a half-acre blaze in remote Lassen Volcanic National Park in Northern California. What became the Reading Fire eventually required firefighters and ended up charring 42 square miles of forestlands as it spread outside the park's boundaries to lands managed by the Forest Service and California Department of Forestry and Fire Protection.

The fire damaged the region's timber industry and cost an estimated $15 million to suppress. No structures were harmed.

While each agency involved had a different approach to managing fires, the confusion during the Reading fire hammered home the need for agencies with different approaches to talk more often about their expectations, a review of the incident found.

Knowing that the Forest Service is stepping back from 2012's more aggressive approach helps different agencies plan how they will respond to fires that have the potential to spread, said Eric Hensel, a National Parks Service fire management officer at the Lassen park.

"What we learned with the Reading fire is that, even with USFS going a little bit further toward (allowing fires to burn), we can't assume anything," Hensel said. "Now we've got some common ground here in terms of our approach, but let's be up front about where we are and work together."