'Heavyweights' joining Iran nuclear talks
22 November 2013 Last updated at 23:21 GMT
The UK's William Hague, US Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov are said to be preparing to join negotiations with Iran over its nuclear programme.
As the talks moved into a third day, Iran said there were "serious issues" to be resolved, while one Western diplomat cited "considerable gaps".
Jeremy Bowen reports from Geneva.