Kerry meets Iranian Foreign Minister Zarif in Munich
No further details were immediately available.
Iran reached a landmark preliminary agreement with six world powers in November to halt its most sensitive nuclear operations, winning some relief from sanctions in return.
Iran is to begin talks with the United States, China, Russia, Britain, France and Germany in Vienna on February 18 on a definitive settlement of the decade-old dispute over its nuclear programme.
(Reporting by Stephen Brown; writing by Alexandra Hudson)