Iranian negotiators and those of the P5+1 group (Britain, China, France, Germany, Russia and the United States) are meeting in Vienna to clinch a deal that would guarantee the strictly peaceful nature of Tehran's nuclear programme in exchange for a lifting of punishing international sanctions.
"The general framework that the Islamic Republic of Iran wants is accepted by the P5+1 group but there are still many differences in the details that must be addressed," Rouhani told a press conference on the occasion of the second anniversary of his election.
Yesterday, a senior Russian official said there had been a "very worrying" slowdown in progress in the talks.
"This is very worrying to us because there is very little time before the deadline and we urgently need to enter the final stage," said chief Moscow negotiator Sergei Ryabkov.
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Rouhani criticised Western countries which he said "haggle" permanently on the terms of the nuclear deal.
"If the other party respects the agreed framework and does not add other demands, the differences can be resolved, but if they choose the path of haggling then it can prolong the negotiations," he added.
The Iranian president also said that "several months will pass" between the signing of the agreement until its implementation.
"We are currently discussing it," said Rouhani asked about the timing of the lifting of international sanctions.
A UN Security Council resolution to cancel previous resolutions on nuclear matters "will be the first major step and a guarantee for the implementation of the agreement," he said.
These sanctions, implemented in 2012, targeted the oil and financial sectors of Iran and plunged the country into a deep economic crisis.
Rouhani said the talks were "so far a great victory for the Iranian nation". The major powers have recognised Iran's right to possess a uranium enrichment programme and the enrichment sites in Natanz and Fordo will remain open, he said.