An agreement on lifting the sanctions imposed on Iran over its nuclear program would be a "giant step" forward after decades of hostility by the United States, according to Ayatollah Akbar Hashemi Rafsanjani, the Islamic Republic's former president, IRNA reported.
Rafsanjani, a close confidante of Ayatollah Khomeini, the leader of the Islamic Revolution, and a heavyweight leader himself for 40 years, hailed Iran's decision to negotiate directly with Washington.
"We have broken a taboo," he told the Guardian in an exclusive interview in his Tehran office.
Rafsanjani is a highly influential supporter of the current president, Hassan Rouhani, whose election in 2013 paved the way for nuclear talks, the daily reported.
He was speaking on Tuesday before it was announced that the Vienna negotiations between Iran, the US and five other world powers had been extended for an additional three days after missing a second deadline. The first deadline on 30 June also passed without agreement.
"Having face-to-face negotiations is better than talking at long distance through the media," Rafsanjani said. "Iran is dead serious. If the other parties are as serious we will have an agreement for sure. That Iran is talking directly to the US is a good move. We have broken a taboo."
Rafsanjani also said US hostility to Iran had long been the main problem.
"Before the  revolution the US was the main supporter of the Shah's regime and after the revolution, in the imposed war [with Iraq] it was against us too. Now in the nuclear talks, if we see a different US, it will have a positive impact on the Iranian public." It was "not impossible" that an American embassy could reopen in Tehran.
"But that depends on the behavior of both sides."