President Hassan Rouhani warned that Iran would scale up its nuclear work if major powers breach their commitments under a possible comprehensive deal.
"If they violate the deal, the government will be fully prepared to go back to the old path so strong that it will be beyond their imagination," IRNA quoted Rouhani as saying.
"Both sides should remain committed to what will be agreed."
He made the remarks in an address to media people in Tehran on Tuesday. Rouhani said achieving the deal depends on whether some parties to the talks will drop excessive demands and respect the Geneva and Lausanne agreements.
"Reaching the comprehensive nuclear accord will be possible within the frameworks of the Geneva and Lausanne agreements, if the other side does not make excessive demands."
A deadline for the final deal between Iran and the P5+1 (the five permanent members of the United Nations Security Council plus Germany) which was due to expire on Tuesday was extended for seven days.
The two sides signed an interim deal in Geneva in late 2013 and reached an agreement on the outline of the prospective final accord in early April in Lausanne, Switzerland.
Rational Approach
Tehran agreed to engage in the talks to demonstrate its rational approach with the world, he said.
"One of our aims in the negotiations is to demonstrate the reality that the Islamic Republic favors logic and seeks to resolve its issues with others at the negotiating table."
Noting that if the deal is reached, the government would not abandon the policies of the resistance economy, he said, "We will follow the path of the resistance economy with all power because it is in the country's interest."
"It is a path that can lead to a boost in the nation's power. If the resistance economy is accompanied by a culture of perseverance and constructive interaction with the world, it will enable us to quickly overcome problems."
The resistance economy is a policy proposed by the Leader of the Islamic Revolution Ayatollah Seyyed Ali Khamenei to counter sanctions, promote domestic growth and reduce consumption.
Under the deal, Iran would see economic sanctions lifted in exchange for accepting temporary constraints on its nuclear program.
Obama Statement
Meanwhile, US President Barack Obama said Iran should respect the terms of the Lausanne agreement, which commit Iran to allowing inspection of its facilities by the UN nuclear agency under the final accord.
"There has been a lot of talk on the other side from the Iranian negotiators about whether, in fact, they can abide by some of the terms that came up in Lausanne," Obama said at a news conference on Tuesday.
"If the inspections regime, verification regime is inadequate then we're not going to get a deal and we've been very clear to the Iranian government about that," he was quoted by Reuters as saying.
Iran has ruled out any inspection of its military sites, but has said it is ready to implement the International Atomic Energy Agency's Additional Protocol, which gives the agency broader access to its nuclear facilities.
