WASHINGTON -- Human rights advocates Wednesday attacked a new Pentagon policy on cluster bombs, saying the military's effort to build a safer version of the controversial weapon was misguided and likely to fail.

The three-page policy, formally released Wednesday, describes cluster bombs, which release tiny bomblets over a relatively wide area, as "legitimate weapons with clear military utility."

But critics say the weapons have a high failure rate. Many bomblets may not explode on contact, and later can be accidentally triggered by civilians.

The new policy is designed to reduce the danger of unexploded bomblets by mandating that bombs with a "dud rate" higher than 1% will not be used after 2018. Until then, the use of a cluster bomb with a higher failure rate must be approved by regional commanders.

"For the U.S. to take another 10 years to eliminate the worst of the cluster munitions is completely inadequate from a humanitarian point of view," said Bonnie Docherty, an arms researcher with Human Rights Watch.

In May, 111 nations, including Britain, endorsed an international ban on the use of cluster munitions. The move was a snub to the United States, Russia, China and Israel, which have opposed prohibitions on use of the munitions.

Each bomb contains several hundred smaller explosive devices, and the U.S. inventory includes a total of about 720 million of the bomblets. The Pentagon adopted a policy in 2005 banning acquisition of cluster bombs with a dud rate higher than 1%, but the inventory contains many munitions purchased before then.

The military has tried to find a weapon that can achieve a failure rate of 1% or lower, said Steve Goose, director of the arms division at Human Rights Watch. "There has been no production of cluster munitions because they cannot meet the standard in the cost range they want," he said.

Human rights groups say that many have a failure rate of 16% or greater, and that even the improved weapons have had a higher failure rate on the battlefield.

"The military and manufacturers' claims are one thing, and the reality of what happens in combat are another," Goose said.

Air Force Lt. Col. Almarah K. Belk, a Pentagon spokeswoman, said certain situations may require the use of cluster bombs, citing as an example the presence of militants on the roof of a building occupied by civilians. A cluster bomb dropped on the roof could kill or injure the militants without destroying the building, she said.

"It is not pretty; nothing about war ever is," Belk said. "It's not always your first choice. . . . But the other alternatives aren't good choices either. They would cause a lot more civilian injury, loss of life, a lot more infrastructure damage."

Goose rejected that scenario, saying the use of a cluster bomb in a populated area should never be permitted.

"You can't target one house. You will be littering the entire area with little land mines," he said.

He said he was puzzled by the new policy because it is at odds with the push to use more precise low-yield weapons.

"It's totally counter to the trend of being ever more concerned with collateral damage," Goose said.

© 2008 The Los Angeles Times