Fresh talks aimed at finalising a nuclear deal between Iran and world powers will focus on the lifting of sanctions and possible intervention by US Congress, a top Iranian negotiator said Wednesday.
Iran and the P5+1 group of nations agreed earlier this month to a framework deal aimed at putting a nuclear bomb out of Tehran's reach in return for an easing of economic sanctions.
US President Barack Obama called the interim agreement a "historic understanding" but Iran is concerned that US Congress could introduce a bill to block a final accord, which must be struck by June 30.
"We will ask the American delegation to explain this issue and will ask for clear and precise information on the details regarding the removal of sanctions," deputy foreign minister Abbas Araghchi told the official IRNA news agency.
He warned that intervention by Congress could have "negative consequences" on the nuclear talks, which were set to resume in Vienna on Wednesday.
"The US is part of multilateral negotiations and it is the responsibility of this government to ensure that its obligations, in particular those related to sanctions, will be implemented in full," Araghchi said.
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If fully implemented, a deal will see Iran dramatically scaling back its nuclear activities and submitting those that remain to what Obama described the "most robust and intrusive inspections and transparency regime ever negotiated".
In return, the United States and five other major powers committed to lift certain sanctions that have caused the Islamic republic of 75 million people major economic pain by strangling its oil exports and financial system.
The accord, if completed and implemented, would draw to a close a crisis that has been steadily and dangerously escalating since Iran's nuclear programme was first revealed some 12 years ago.
Araghchi, who is leading the Iranian delegation, said that "the lifting of sanctions should not be linked to conditions unrelated" to Tehran's nuclear activities, such as its ballistic missile programme.
Iran, subject to international economic penalties since 2006, wants complete sanctions relief once a deal is struck.
But world powers insist this shall only occur once the nuclear inspectors confirm that Iran is keeping its side of the bargain.
Iranian foreign ministry spokeswoman Marzieh Afkham said on Wednesday that there was a "possibility of changes in the terms" of the framework agreement thrashed out in Lausanne.
"If there were not going to be changes, it would be pointless to continue the negotiations," she told reporters in Tehran.