Some enduring differences between Iran and the West over the nuclear programme of the country have hindered the progress in preparing the draft for a possible nuclear agreement, Iran's senior nuclear negotiator Abbas Araqchi said.
"In the recent round of talks, both sides reviewed all issues, however, differences still remain," Islamic Republic News Agency quoted Araqchi as saying on Saturday.
He made the remarks following two rounds of meetings between US Secretary of State John Kerry and his Iranian counterpart Mohammad-Javad Zarif in Geneva.
Earlier in the day, Araqchi said that details and implementation of the additional protocol to the Non-Proliferation Treaty (NPT) would be a major condition for the nuclear agreement ahead of the self-imposed June 30 deadline.
Iran has emphasised that it would not allow International Atomic Energy Agency inspectors to have access to its military sites under the additional protocol to the NPT.
Iran and the world powers resumed a new round of negotiations on Wednesday in a bid to finalise an accord on Tehran's disputed nuclear programme.
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The next round of nuclear talks between the representatives of Iran and the P5+1 countries -- the US, Britain, France, Russia, China and Germany -- will be held on Thursday in Vienna, Araqchi said on Saturday.
The late June deadline was agreed by the negotiators in November 2014 after a failed attempt to reach a comprehensive nuclear deal as the parties were divided over limiting Iran's uranium capacity and steps to lift sanctions that are crippling the Iranian economy.