GENTHOD, Switzerland - Iran and six world powers put nuclear talks back on track at a landmark session that included the highest-level bilateral contact with the U.S. in years. The meeting ended with a pledge to meet again this month, but disputes surfacing shortly after its conclusion indicated a rough road to agreement ahead.

Iran accepted a demand Thursday at the talks in a villa outside Geneva to allow U.N. inspectors into its covertly built enrichment plant, in a move that appeared to defuse tensions that had been building for weeks.

Western officials at the session said the Islamic republic had also agreed to allow Russia to take some of its enriched uranium and enrich it to higher levels for its research reactor in Tehran, a potentially significant move that would show greater flexibility by both sides...