The $410 billion spending bill U.S. President Barack Obama signed Wednesday includes a provision that outlaws exports of cluster bombs unless they leave behind 1 percent or less of their submunitions as duds and the receiving country agrees the weapons "will not be used where civilians are known to be present."
The provision makes permanent a one-year ban enacted in December 2007, officials said.
Obama's stand "brings Washington into closer alignment with international opinion on this terrible weapon," Human Rights Watch arms division Director Steve Goose said.
But Obama should now support an international treaty prohibiting the use of cluster bombs that could threaten civilians, the rights group said.
"If it is unacceptable for foreign militaries to use these weapons, why would it be acceptable for the U.S. military to use them?" Goose asked.
As a senator, Obama voted for a 2006 amendment to a defense spending bill that would restrict cluster bomb use in civilian areas, but the amendment was defeated, Congressional Quarterly reported.
His transition team said last fall Obama would study the issue. Sixty-seven human rights groups urged Obama last month to begin the review and complete it within six months.
Cluster bombs are air-dropped or ground-launched munitions that eject hundreds of "bomblet" clusters in midair that scatter randomly over a wide area.
These bomblets often don't explode, littering war zones with de facto land mines that kill civilians long after a conflict ends.