The foreign minister stressed that Iran is after a "fair" and "balanced" agreement in nuclear negotiations with major powers, which slid past a Tuesday deadline for a final settlement.
"The only deal that the Iranian people will accept is one that is fair and balanced and (preserves) national dignity and the nation's rights," Mohammad Javad Zarif told reporters upon arrival in Vienna on Tuesday.
"I believe it is a reality acknowledged by the other side that a long-term agreement is impossible if it fails to recognize the nation's rights," IRNA quoted him as saying.
Zarif flew back after departing the Austrian capital for Tehran on Sunday.
He was accompanied by Atomic Energy Organization of Iran director Ali Akbar Salehi and Hossein Fereydoon, a brother and close aide to President Hassan Rouhani.
"As we have always said the negotiations must be based on a logical balance. All Iranian officials have been voicing readiness for reasonable and logical negotiations and a trade-off."
"If (the talks) are followed based on the Lausanne agreement, it will be possible to achieve solutions," he noted.
Iran and the P5+1 (the five permanent members of the UN Security Council plus Germany) reached a preliminary agreement on April 2 in Lausanne, Switzerland.
Diplomats say Salehi and his US counterpart Energy Secretary Ernest Moniz played a key role in drawing up the framework agreement in Lausanne.
"Mr. Salehi is of great assistance to us …. He can help address many of the (remaining) gaps (in the talks)," Zarif said.
Negotiations have reached a "critical" stage and it is essential that the other side show "political will" to ensure an "acceptable" and "lasting" deal, the chief negotiator added.
An unnamed negotiator told reporters on Tuesday, "Given several outstanding differences, the negotiations will continue over the coming days."
He added, "It has not been decided for how many more days (the talks will go on)." There has not been any discussion yet about a long extension of the deadline.
Tuesday saw bilateral meetings between Zarif and his US counterpart John Kerry, Russian Foreign Minister Sergey Lavrov and International Atomic Energy Agency Director General Yukiya Amano.
***National Factsheet
A national nuclear factsheet bearing the signatures of millions of Iranians was put on public display at Azadi square in Tehran on Tuesday, reemphasizing the red lines in the negotiations.
According to the factsheet, all sanctions must be terminated, rather than suspended, at once and simultaneously with the signing of the deal.
Nuclear achievements must be preserved and boosted to the extent that the real needs of the country are met.
No restriction is acceptable on continued nuclear research and development and nuclear scientists.
Any extraordinary monitoring of military and security centers and personnel is also prohibited.
