evidence: The United States reached agreement with Uzbekistan yesterday to begin providing technical assistance for cleaning up a former Soviet biological weapons test range on an island in the Aral Sea that is heavily contaminated with anthrax spores, a State Department official said. The official said the United States has grown increasingly concerned about the lethal material left on the island, which belongs jointly to Uzbekistan and Kazakhstan, because the surrounding sea is drying up. The site, dubbed the world's largest anthrax burial ground, may soon be accessible by a newly formed land bridge, presenting both environmental and security challenges.