United States' President Barack Obama says he is optimistic a comprehensive accord to curb Iran's nuclear program will be finalized despite strong words this week from the country's Supreme Leader Ayatollah Ali Khamenei.
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Radio Free Europe/Radio Liberty: Obama upbeat on final iran nuke deal
US Secretary of State John Kerry (L) and his Iranian counterpart Mohammad Javad Zarif pose before resuming talks over Iran's nuclear programme in Lausanne on March 16, 2015.
