President Hassan Rouhani said on Sunday Iran will not abandon its nuclear rights, including uranium enrichment, media reported a day after a fresh round of talks with world powers.
"There are red lines that must not be crossed," Rouhani told the conservative-dominated parliament in remarks quoted by the ISNA news agency.
"The rights of the Iranian nation and our national interests are a red line. So are nuclear rights under the framework of international regulations, which include enrichment on Iranian soil," he said.
His remarks came a day after intensive negotiations with world powers -- despite making progress -- failed to produce a long-elusive deal that would curb Iran's nuclear activities in exchange for sanctions relief.
Hopes had soared after top world diplomats rushed to Geneva to join the talks, but then faded as cracks began to appear among world powers when France raised concerns.
The P5+1 group in the talks -- Britain, China, France, Russia and the United States plus Germany -- suspects that Iran's atomic ambitions are aimed at developing nuclear weapons, despite repeated denials.
Rouhani pleaded for parliament's backing.
"If we want to succeed in these negotiations, we need the support of the supreme leader (Ayatollah Ali Khamenei) and of lawmakers," he told them.
With the final say on the nuclear issue, Khamenei had expressed support for Iran's negotiators but also voiced pessimism about the possibility of a breakthrough, citing decades of hostility and mistrust in the West.
Hardliners in Iran had also been sceptical, fearing that the negotiating team led by Foreign Minister Mohammad Javad Zarif would offer too many concessions.
Rouhani said Iran would "not bow to threats from any power", while also insisting that sanctions battering Iran's ailing economy had not forced it to the negotiating table.
"We have practically and verbally told the negotiating sides that threats, sanctions, humiliation and discrimination will never produce a result," he said.