WASHINGTON (Reuters) - The Pentagon is tripling its spending to about $3.5 billion, on a newly expanded effort to combat the rising number of increasingly powerful homemade bombs that are the No. 1 killer of U.S. troops in Iraq, The New York Times reported on its Web site on Sunday.

The move is a tacit acknowledgment that despite years of rising death tolls from the devices, the response has not been sufficiently focused or coordinated at the highest levels, the Times said.

Last year, 407 of the 846 Americans killed in Iraq were killed by the bombs, which are called improvised explosive devices (IEDs), the report said. The number of IEDs against allied and Iraqi forces and Iraqi civilians nearly doubled last year from 2004 to 10,593.

The intensified effort to combat the makeshift bombs, which at one time was led by a one-star general, was recently put under a retired four-star Army general, Montgomery Meigs, the Times said, citing interviews with a dozen military officials.

In the next few months, the Defense Department plans to double the number of technical, forensic and intelligence specialists assigned to the problem, to about 360 military service members and contractors in the United States and Iraq, the paper said.

Hundreds of other experts are being called in and new technology and training techniques are also quickly being pushed into service, The Times reported.

Some of the most deadly bombs use shaped charges, which penetrate armor by focusing explosive power in a single direction and by firing a metal projectile embedded in the device into the target at high speed.

In 2005, the budget for the Pentagon's IED task force was $1.2 billion, double the previous year's. The details of this year's budget are still being refined, at about $3.5 billion, but senior officials say they essentially have a blank check, The Times said.