Geneva ? U.S. officials said Monday they are willing to negotiate a treaty on the use of cluster bombs, reversing their position that no new agreement on the weapon was necessary.

But the United States still rejects a proposed global ban on the weapon, which 46 countries began negotiating in Oslo in February, officials said. Instead, Washington wants to negotiate a treaty that doesn’t go as far within the framework of the 1980 U.N. Convention on Conventional Weapons.

Ronald Bettauer, head of the U.S. delegation, said the U.S. position has changed “due to the importance of this issue, concerns raised by other countries, and our own concerns about the humanitarian implications of these weapons.”

The U.S. said in November there were sufficient controls on the weapon in existing treaties. And it has said cluster bombs, used carefully, have important military uses, such as attacking artillery positions, armored columns and missile installations.

The U.S. still insists on the military use of cluster bombs, but wants to limit the impact they have on civilians and improve their accuracy.

Fired by artillery or dropped by aircraft, cluster bombs are canisters that open in flight and eject dozens or hundreds of small “bomblets” across a wide area. Those that do not explode right away may detonate later, experts say.

Children are especially vulnerable because the bomblets are often an eye-catching yellow with small parachutes attached.

The United Nations has estimated that Israel dropped as many as 4 million of the bomblets in southern Lebanon last summer, with perhaps 40 percent of the submunitions failing to explode on impact.

No international treaty specifically forbids the use of cluster bombs, though the Geneva Conventions outline laws protecting civilians during conflict. Because cluster bomblets often cause civilian casualties after conflicts end – much like land mines – their use has been heavily criticized by human rights groups.