Negotiators optimistic, but impasse remains over UN sanctions, future atomic research

Major powers and Iran were closer to a preliminary accord on reining in Teheran's nuclear program as marathon talks ran into Wednesday, but they hit an impasse over key details such as the lifting of UN sanctions and Iran's future atomic research.

The negotiators ended talks in the Swiss city of Lausanne in the early morning hours with an air of chaos as delegations scrambled to get contradictory viewpoints across.