Iran's president has said Tehran wants an international settlement over its nuclear programme but will never give up uranium enrichment.
The remarks by Hassan Rouhani repeat past declarations over the country's "right" to produce nuclear fuel, as he seeks to assure critics that Iran will not make sweeping concessions in negotiations with world powers.
Talks ended in Geneva with all sides proclaiming progress but noting obstacles such as France's worries over Iran's enrichment levels and a planned heavy water reactor that produces plutonium by-products. Negotiations resume next week.
Mr Rouhani was quoted by the semi-official ISNA news agency as telling parliament that uranium enrichment is a "red line" that cannot be crossed.
The West suspects Iran's nuclear programme has a military dimension but Iran denies the charge.
Iran's foreign minister Mohammad Javad Zarif, in a posting on his Facebook page, said there are "some problems" still to overcome but called the latest round of negotiations with the six-nation group - the five permanent UN Security Council members plus Germany - "serious but respectful".
The West and its allies fear Iran's uranium enrichment labs could one day produce weapons-grade material.
But, in an important shift, the US and others no longer appear to demand a complete halt to enrichment and are concentrating on curbing the highest-level production, currently at 20% .
Such material is needed for Iran's lone research reactor, which makes isotopes for medical treatments, but is only just several steps away from warhead level at more than 90% enrichment. Energy-producing reactors use uranium enriched at levels of about 3.5%.
Iran insists it does not seek nuclear weapons and says its reactors are only for electricity and medical applications.
In an address to parliament, Mr Rouhani said uranium enrichment is a "red line" that cannot be crossed.
"Nuclear rights in the international framework, including uranium enrichment, on its soil" are not negotiable, Mr Rouhani said. "For us red lines are not crossable."
Iran claims it cannot be forced to give up enrichment because it has signed a UN treaty governing the spread of nuclear technology. The pact allows for enrichment under UN monitoring.
Israeli prime minister Benjamin Netanyahu has criticised what he considers readiness by the six powers to be too generous to Tehran for not enough in return. The US and others are considering easing economic sanctions in return for a possible suspension in 20% enrichment.
Mr Rouhani said Iran is similar to other countries and "we are not ready to accept discrimination, at all".
"We have told the other party that threats, sanctions, humiliation and discrimination will not lead to an answer," said Mr Rouhani.
In the latest Geneva rounds, which began on Thursday, there were growing expectations of an accord. France, however, would not soften its concerns, claiming the deal offered did not go far enough to trim Iran's nuclear programme.
French foreign minister Laurent Fabius told France-Inter Radio that his nation does not want to be part of a "con game". He did not elaborate, but it appeared France wanted tougher constraints on a reactor that will make plutonium when completed, and on parts of Iran's uranium enrichment programme.
The plutonium byproduct from the reactor can be used to make nuclear weapons, but the process to extract it requires specific technology that Iran currently does not possess.
As the talks foundered after initial signs of progress, U.S. Secretary of State John Kerry rushed to Geneva on Friday, followed by counterparts from Russia, China, Britain, France and Germany, to try to push through an agreement.
Mr Kerry said "significant progress" had been made on the remaining differences, but noted there were "certain issues that we needed to work through". The next round of talks is set for November 20.
It was later announced that UN nuclear chief Yukiya Amano is heading to Tehran as part of efforts to investigate suspicions that Iran worked secretly on nuclear weapons.
Those attempts have been stymied by nearly two years of arguments over what can be seen, and who can be interviewed how many times by Mr Amano's experts.
Iran in the past rejected the open-ended investigation that Mr Amano seeks. But Iran's new leadership has promised more cooperation than in the past.
Mr Amano said "we aim to build" on new ideas presented by Iran.