"What happens in the US Congress, that's certainly a US issue," he told a news conference in Tunisia.
"We believe it's a mutually beneficial agreement," Zarif said of the July 14 accord on scaling down Iran's controversial nuclear programme in exchange for a lifting of international sanctions.
And if people are not too much concerned with the propaganda being raged by warmongers in our region and outside our region, there's no reason for the deal to face any impediments in the US," said the minister who negotiated the deal.
Republicans strongly oppose the deal, saying it makes too many concessions to the Islamic republic and does so at the expense of the security of America and its chief ally Israel.
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If the Republican-dominated Congress passes a resolution against the deal, President Barack Obama is expected to veto that move.
On the battle against the jihadist Islamic State (IS) group, in which arch-foes Tehran and Washington find themselves on the same side, Zarif called for a "multi-faceted" campaign.
"It has to be a multi-faceted cultural, religious, political, economic and if necessary military campaign against this threat," he said.
"We need to uproot the sources and the main reasons that give rise to this phenomenon."
IS has claimed responsibility for two major attacks in Tunisia this year in which 59 foreign tourists and a policeman were killed.