A senior Russian diplomat says if there’s a will in Washington & Tehran, a deal could be reached soon.
While all sides agree to keep talking, little progress has been made in overcoming significant disagreements.
The warning was issued at a board meeting of the UN’s International Atomic Energy Agency in Vienna.
The US last week penalised a number of Iranian and foreign companies for violating sanctions against Tehran.
All sides agreed to continue talking for four more months to try reach a final agreement.
US Secretary of State John Kerry met Irain’s Mohammad Javad Zarif on Tehran’s nuclear programme.