After years of resisting limits on laser weapons, the Defense Department has abruptly shifted position, prohibiting lasers designed to blind foes permanently and agreeing to international negotiations on banning use of such weapons.

The move by Defense Secretary William J. Perry was welcomed by members of Congress and human rights activists critical of the Pentagon’s previous stance. But they said the Pentagon’s turnaround did not go far enough and called for a ban on purposefully using any lasers to blind, not just a prohibition on lasers designed for that purpose.

Military lasers have become a focus of growing international attention as advances in technology have led to easier applications and wider use. In a study earlier this year, Human Rights Watch, an independent watchdog group, warned lasers were opening a “grotesque new chapter in warfare.”