U.S. says talks intense, serious after Iran hints at atomic concessions

GENEVA (Reuters) - The United States described two days of nuclear negotiations with Iran as the most serious and candid to date after Western diplomats said Tehran hinted it was ready to scale back sensitive atomic activities to secure urgent sanctions relief.

But a senior U.S. administration official told reporters after the conclusion of negotiations between Iran and six world powers that no breakthroughs had been achieved and many disagreements remained. Other Western diplomats involved in the talks said there had been no apparent narrowing of differences between Tehran and the six nations over its nuclear ambitions.