The first round of nuclear talks between Iran and the P5+1 group which was launched in Vienna earlier on Tuesday "is a new beginning of cooperation between the two sides," an Iranian official said.Abbas Araghchi, Deputy Foreign Minister and member of the negotiating team, said "tough and long negotiations" would be facing the two sides.Tehran is determined to continue negotiations in an atmosphere of mutual confidence, Aragchi told reporters after the end of the first round.Iranian Foreign Minister Mohammad Javad Zarif was heading his country side while Catherine Ashton, the EU's foreign policy chief, was heading the P5+1 group - the US, Russia, China, France, Britain and Germany.The talks aimed at reaching a final agreement deeming the Iranian nuclear program peaceful and lifting sanctions imposed on the Islamic Republic. The two sides had reached an interim agreement in Geneva last November.Aragchi said this round of negotiations was based on the Geneva accord, and the two sides would not discuss any issue outside the framework of that agreement.He said Zarif was holding bilateral meetings with the three European countries and the US, and the rest of official negotiations would continue to be chaired by Aragchi and Ashton, and would be attended by political directors of the P5+1 group and experts.Zarif, speaking to reporters after arrival in Vienna last night, expressed optimism the two sides would achieve progress towards a final agreement.