"The internal issues (of Iran) were not raised during the meetings (with Kerry) at all and the report released with regard to this issue is a sheer lie," Zarif said on Saturday.
Reuters reported on Saturday that Zarif had warned the US that failure to agree a nuclear deal would likely herald the political demise of pragmatist President Hassan Rouhani, raising the stakes as the decade-old stand-off nears its end-game.
"Zarif pressed the concern with US Secretary of State John Kerry at several meetings in recent weeks, according to three senior Iranian officials, who said Iran had also raised the issue with other Western powers. Zarif's warning has not been previously reported," Reuters added.
According to Reuters, the western officials acknowledged that the move may be just a negotiating tactic to persuade them to give more ground, but said they shared the view that Rouhani's political clout would be heavily damaged by the failure of talks.
The report came after Zarif underlined on Saturday that a final deal on Tehran's nuclear issue required the West's political will, adding that the country doesn’t negotiate under pressure.
"Iran will never even enter talks under pressure, let alone making an agreement," Zarif told reporters after ending his African tour.
Zarif said "the problem lies with the political decision" that the western states should make and show if they, "specially the US, want to settle the issue or want to pressure Iran".
He expressed pleasure that the westerners have themselves come to realize that sanctions are not effective and will further increase the Iranian nation's pessimism about the West, and said, "I feel that they have fully understood this, and accordingly, we hope that we can reach results."
Asked about the trend of talks between Iran and the Group 5+1 (the US, Russia, China, Britain and France plus Germany), he said, "the nuclear negotiations are now dealing with details of technical issues, meaning that today we will discuss the issue of enrichment."
The 10th round of negotiations between Iran and the six world powers was held in Vienna from November 18 to 24, where the seven nations decided to extend the talks until July after they failed to strike an agreement.
The latest round of the nuclear talks between the two sides was held at the level of deputy foreign ministers in Geneva, Switzerland, on January 18.
The two sides decided to continue their talks in February.
Both Iran and the G5+1 negotiators have underlined that cutting a final deal before the July 10 deadline is possible
