Ali Akbar Velayati said staying or leaving "depends on the Americans".
Velayati was responding to U.S. Secretary of State John Kerry. Kerry said President Barack Obama was "fully ready" to pull the U.S. out before agreeing to a deal.
Earlier, Foreign Minister Muhammad Javad Zarif said Iran will accept either an overarching nuclear agreement or no agreement at all.
Zarif said Tehran would not approve of an "incomplete and vague" nuclear accord, but rather a "complete agreement".
"No other deal will be reached before a complete agreement is clinched," said the top diplomat.
Zarif also referred to the discussions at the deputy ministers level between the Islamic Republic and the United States in Geneva on Friday.
"The deputies had good discussions, but no particular agreement has been made on the issues.”
Zarif and Kerry were scheduled to join the talks on Sunday and hold discussions for two days.
Kerry said there are still "significant gaps" in negotiations, adding Obama was not prepared to extend them further.
Negotiators are working against the clock ahead of a March 31 deadline for agreement on the political framework of a deal.
"There are still significant gaps, there is still a distance to travel," Kerry told a press conference at the U.S. Embassy in London.
"President Obama has no inclination whatsoever to extend these talks beyond the period that has been set out."
He added that Obama was "fully prepared to stop these talks" if necessary.
U.S. Energy Secretary Ernest Moniz flew in to snow-covered Geneva on Saturday to take part in the talks for the first time, and at Kerry's request.
But Kerry played down any suggestion that this meant the talks were on the verge of a breakthrough.
"I would not read into it any indication whatsoever," he said, adding that Moniz was present because of the "technical" nature of the talks.
Salehi arrived Saturday morning with Zarif and Hussein Fereydoun, the brother and special aid to Iranian President Hassan Rouhani, to help coordinate the talks, Iranian media reported.
Iranian officials have voiced unhappiness with separating the political and technical aspects of an agreement.
"We won't have a two-stage deal," Deputy Foreign Minister Abbas Araghchi said.
"After a year of negotiations, we must tackle the details and all the more so as we want to have both the general framework and the details in the final agreement."
A key stumbling block in any final deal is thought to be the amount of uranium Iran would be allowed to enrich, and the number and type of centrifuges Tehran can retain.
American conservative political columnist Pat Buchanan said Iran is not developing nuclear bombs or intercontinental ballistic missiles.
"There is no bomb program going on, according to our intelligence…I don’t believe there is an intercontinental ballistic missile being developed by Iran.”