Kerry to join troubled nuclear talks as Iran refuses to give ground on key Arak reactor

U.S. Secretary of State John Kerry will join troubled nuclear talks in Vienna later Nov. 20, as Tehran showed no sign of softening its position days before a deadline for a deal.

The announcement of Kerry's trip came a day after his counterpart from Britain, one of six powers negotiating with Iran ahead of the cut-off point on Nov. 24, expressed pessimism that the mammoth accord could be done in time.

"I am not optimistic that we can get everything done by Monday," British Foreign Secretary Philip Hammond said in Latvia.        

The best to be hoped for, he indicated, was another extension, but only if there is "significant movement."

A U.S. State Department spokesman however insisted that negotiators were "still focused" on getting a deal done in time - something that many experts doubt, particularly as an earlier July 20 deadline was missed.

Iran and the five permanent members of the U.N. Security Council plus Germany have been negotiating since February to turn an interim accord with Iran reached a year ago into a lasting agreement before November 24.

Such a deal, after 12 years of rising tensions, is aimed at easing fears that Tehran will develop nuclear weapons under the guise of its civilian activities - an ambition the Islamic republic has always denied.
                      
Some areas appear provisionally settled in what would be a highly complex deal that would run for many years, even decades.

But two key issues remain: enrichment - rendering uranium suitable for peaceful uses but also, at high purities, for a weapon - and the pace of the lifting of sanctions on Iran under a deal.

Iran's nuclear chief on Nov. 20 ruled out further negotiations on the design of a reactor that...