The Bush administration has blamed environmental groups for contributing to the US forest fires by blocking the federal government’s effort to remove underbrush.

But WWF-US says it is a century of logging, livestock grazing, road building and indiscriminate fire suppression that has primed the forests for such intense fires.

It is calling for solutions including controlled burns, thinning in tree plantations and protection for roadless forests to reverse the situation.

The US government says green groups have repeatedly gone to court to challenge the US Forest Service‘s attempts to thin out forests by letting timber companies cut trees.

The US is facing one of its worst fire seasons in recent years.

The Forest Service says that more than 2.5 million acres (1 million ha) have burned this year, nearly 1.2 million acres (485,000ha) more than at the same time in 2000.

Nearly 20 large fires are being battled in nine western states and federal aid has been made available to parts of Arizona. Colorado has also been declared a disaster area.