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US Secretary of State John Kerry leaves Palais Coburg where closed-door nuclear talks with Iran take place in Vienna, Austria, Friday, Nov. 21, 2014. Image Credit: AP

Vienna: With three days to go to the deadline for a deal to defuse stand-off with Iran over its nuclear ambitions, Western power foreign ministers stepped away for consultations on Friday while Tehran’s chief envoy cancelled plans to leave the negotiations.

The United States, Britain, France, Germany, Russia and China began the final round of talks with Iran on Tuesday, looking to clinch a pact under which Tehran would curb its nuclear work in exchange for a lifting of economically crippling sanctions.

But officials close to the negotiations in Vienna said at mid-week the two sides remained deadlocked on key issues, were unlikely to secure a definitive accord by November 24, and might need to extend the deadline.

Russian Foreign Minister Sergei Lavrov and Kerry agreed “additional efforts” were needed to reach a deal by the self-imposed deadline, Russia’s Foreign Ministry said.

“The sides did not rule out the possibility of holding a ministerial meeting of the parties to the talks on Iran’s nuclear programme, if the prospect for progress appears,” the ministry said.

British Foreign Secretary Philip Hammond said after separate meetings with big power peers: “These are complex issues and there are still significant gaps between the parties. We’re all going away to have technical discussions with our experts and we’ll resume again over the ... weekend.”

Iranian Foreign Minister Mohammad Javad Zarif cancelled announced plans to return to Tehran for top-level discussions with the deadline looming.

A source close to the talks said Zarif had received a document from the powers outlining the main principles of a possible agreement on removing sanctions on Tehran in exchange for limits on its nuclear programme.