GENEVA, Nov 23 (Reuters) - Talks on Iran's nuclear programme were "not a done deal," German Foreign Minister Guido Westerwelle said on Saturday, as foreign ministers of six world powers gathered in Geneva for a fourth day of negotiations.

"It's not a done deal. There's a realistic chance, but there's a lot of work to be done," Westerwelle said on arriving in Geneva. (Reporting By John Irish; editing by Justyna Pawlak)