Iran's nuclear chief told AFP Thursday that he was "optimistic" about reaching a nuclear deal with world powers despite interference from those opposed to resolving the long-running crisis over Tehran's atomic activities, AFP reported.
Speaking on the sidelines of crunch talks in Switzerland Ali Akbar Salehi also said Iran was open to show more transparency with its nuclear facilities to ease "fictitious" concerns that it might develop nuclear weapons.
"On the whole I am optimistic... but internationally those who have an interest in more troubles and not dealing with this question have not been inactive. They are trying to make sure there is no deal," Salehi said.
"The Islamic Republic of Iran has demonstrated its political will and it is up to the other side to take a step forward and show that it has the political will to allow a resolution of the problem," Salehi told AFP.
Salehi did not specify which countries he meant but Iran's arch foe Israel is known to be hostile to the agreement that looks to be emerging from 18 months of talks since the 2013 election of President Hassan Rouhani.
Israel, widely believed to have nuclear weapons itself, worries that the accord will not do enough to stop Iran one day getting the bomb, a concern shared by US Republicans as well as Gulf monarchies including Saudi Arabia.
Salehi is a key member of Iran's negotiating team in the talks between senior officials from Iran, the United States and five other world powers including US Secretary of State John Kerry and Iranian counterpart Mohammad Javad Zarif.
Having failed twice in 2014 to reach a deal reining in Iran's nuclear programme in exchange for lifting painful international sanctions, the parties have set themselves a March 31 target to agree the outlines of an accord. A final agreement is meant to be concluded by June 30.
Kerry is under severe pressure from the US Congress to return from Lausanne with something concrete but it is unclear how detailed the "framework" accord will be, or even whether it will be a written document.
Salehi, a former foreign minister who studied nuclear engineering in the United States, said that there remains "work to do and there needs to be answers on certain issues that haven't been clear until now."
Ahead of discussions with US Energy Secretary Ernest Moniz, Salehi said that a range of technical, legal and political aspects needed to somehow fit together in what would be a highly complex agreement.
"Everything is linked. On the technical questions we have come closer together towards a common understanding," he said. "But there remains a lot of work to do."
Salehi also said that Iran would not abandon its "right" to a peaceful nuclear programme but that Tehran was open to more oversight if this is within the rules of the UN atomic watchdog, the International Atomic Energy Agency.
"To answer the fictious concerns of the other side we have declared that we are ready for measures within the rules of the agency (the IAEA) so that these worries are assuaged," Salehi said.
Iran, unlike Israel, is subject to close IAEA tabs, but even tighter inspections by the Vienna body are a key element in the mooted deal.
This would provide added certainty that the Islamic republic has no secret nuclear sites for a clandestine effort to make a bomb, an aim it strenuously denies having.