Iran’s foreign minister has warned the US that any agreement on Iran’s nuclear programme would have to be immediate and unconditional.
Speaking on the sidelines of a meeting of foreign ministers from the six-country group – known as the P5+1 – Mohammad Javad Zarif said that the US should not impose any condition on the agreement.
He was referring to US President Donald Trump’s demand that Iran should abandon the programme.
Talks over the programme resumed on Saturday.
The P5+1 nuclear deal was struck in 2015 and reached after a hard negotiation among US, UK, China, France, Russia and Germany.
On Friday, Iran and the five other states welcomed fresh talks with the US as they try to salvage the 2015 nuclear deal with Iran, which appears under threat from US President Donald Trump.
German Foreign Minister Sigmar Gabriel said the talks were important to keep the deal “on track”.
Mr Gabriel told reporters that an agreement must lead to “a solution that meets the expectations of all” at a news conference in Vienna with Mr Zarif.
Mr Trump is under pressure to toughen his stance on the deal reached in 2015 between Iran and the P5+1 countries.
He has said he does not trust Iran’s commitment to not seeking a nuclear weapon, and wants them to abandon their programme.
Tensions have risen recently between Iran and the US, with both sides exchanging nuclear barbs.
Earlier this month, Mr Trump accused Iran of testing a new missile, days after Iran said that Mr Trump’s dismissal of the 2015 deal was “illogical”.
Officials from the six states involved in the 2015 accord – China, France, Russia, the UK, the US and Germany – will meet again in Vienna, for talks on Iran’s nuclear programme, US officials said.
The foreign ministers of the participating states, along with senior Iranian officials, are expected to meet for two days of talks starting on Saturday, the sources said.
Iran has repeatedly described the 2015 nuclear deal as a law and said it would stay in it until the US Congress lifted its own economic sanctions on Tehran.
Despite the US demands, a UN nuclear watchdog has repeatedly said that Iran has been complying with the 2015 deal since it was signed.
Meanwhile, new US sanctions imposed in February mean foreign companies dealing with Iran can face punitive sanctions.
Mr Trump has said those who defy US sanctions risk being cut off from the US market, but lawmakers have assured foreign companies they will be permitted to continue trading with Iran.
Other members of the agreement remain wary of Washington’s attitude and Tehran could face sustained backlash should it violate the deal, which provides a path to lifting international sanctions against it over its nuclear programme.
Negotiations over the agreement are at a sensitive stage, amid reports that officials from Iran are holding talks with Russia about ending their economic dependence on Tehran, AFP news agency reports.
Senior Iranian nuclear officials have met Russia’s deputy foreign minister, Sergei Ryabkov, in Vienna this week over a possible phased withdrawal from the nuclear deal.
An unnamed Iranian official told the news agency that “resorting to a policy of self-reliance” would free Iran from US sanctions and block it from being cut off by the US.
In recent months, Iran has said it may reinstate its uranium enrichment capability, although these have not yet been confirmed.
International sanctions were lifted in January 2016 after International Atomic Energy Agency (IAEA) inspectors said Iran was abiding by the agreement.
Since the end of last year, the country has been able to sell its oil independently.
Sanctions also apply to Iranian financial institutions, which means European businesses are barred from doing business with Iran, while US companies can invest there but must face American sanctions in the event of a recoupling of US and Iranian currencies.