Iranian Foreign Minister Abbas Araghchi on Sunday ruled out Tehran ever giving up uranium enrichment in its negotiations with Washington, insisting it will not be intimidated by the threat of war with the United States.
Washington first threatened to intervene over Tehran's deadly crackdown on anti-government protesters, with authorities on Sunday arresting three prominent reformists accused of anti-government rhetoric.
They also imposed another hefty prison sentence on Nobel laureate Narges Mohammadi, who was arrested before the protests, on charges of harming national security.
Araghchi told a forum in Tehran attended by AFP that Iran had little trust in Washington and doubted that the US side was taking renewed negotiations seriously.
He later said Iran was consulting with its "strategic partners" China and Russia about the talks.
"Why do we insist so much on enrichment and refuse to give it up, even if a war is imposed on us? Because no one has the right to dictate our behaviour," Araghchi said at the forum.
"Their military deployment in the region does not scare us," he added, referring to the arrival of an aircraft carrier, the USS Abraham Lincoln, in the Arabian Sea.
The United States and Iran reopened negotiations on Friday in Oman for the first time since Israel's 12-day war with the Islamic republic in June of last year, which the US briefly joined.
Iran is seeking to have US economic sanctions on the country lifted, in exchange for what Araghchi said at the forum could be "a series of confidence-building measures concerning the nuclear programme".
Western countries and Israel, thought to be the Middle East's only country with nuclear weapons, say Iran is seeking to acquire an atomic bomb, which the Islamic republic denies.
"They fear our atomic bomb, while we are not looking for one. Our atomic bomb is the power to say 'no' to the great powers," Araghchi said.
The US and Israel want the negotiations to go beyond the nuclear question and include Iran's ballistic missiles and support for armed groups in the region, issues Iran refuses to include in the talks.
- 'Peace through strength' -
Washington's lead negotiators, envoy Steve Witkoff and presidential son-in-law Jared Kushner, visited the nuclear-powered USS Abraham Lincoln on Saturday, the US military's Central Command (CENTCOM) said.
The ship was dispatched to the Middle East several weeks ago as part of military build up in the region, following US President Donald Trump's threats against Iran.
In a social media post, Witkoff said the carrier and its strike group were "keeping us safe and upholding President Trump's message of peace through strength".
The threat of war continues to hover over the negotiations, even as Trump called the talks "very good" and Iran's President Masoud Pezeshkian said they "constitute a step forward".
Following Friday's first round in Oman, Trump signed an executive order calling for fresh tariffs on countries still doing business with Iran.
The United States also announced new sanctions against numerous shipping entities and vessels, aimed at curbing Iran's oil exports.
At the Tehran forum on Sunday, Araghchi said ongoing "sanctions and military actions raise doubts about the seriousness and readiness of the other side to conduct genuine negotiations".
- Arrests, sentencing -
The talks between the two foes and the US military buildup in the region follow Iran's crackdown on anti-government protests that began in late December, sparked by economic grievances.
Iranian authorities on Sunday arrested three reformist figures including the head of Iran's Reform Front coalition, Azar Mansouri, the Fars news agency reported, listing charges that included "targeting national unity" and "coordination with enemy propaganda", among others.
After the demonstrations began, Mansouri posted on Instagram that "when all avenues to be heard are closed, protest takes to the streets", later calling the death toll a "great disaster".
Meanwhile, jailed Iranian Nobel Peace Prize winner Narges Mohammadi was sentenced on Saturday to six years in prison on charges of harming national security and one-and-a-half years for "propaganda" against Iran's Islamic system, her foundation said in a statement.
She was arrested after speaking out against the government at a funeral ceremony in December.
The authorities in Iran have acknowledged that 3,117 people were killed in the protests, publishing on Sunday a list of 2,986 names, most of whom they say were members of the security forces and innocent bystanders.
International organisations have put the toll far higher.
The US-based Human Rights Activists News Agency (HRANA) says it has verified 6,961 deaths, mostly protesters, and has another 11,630 cases under investigation.
It has also counted more than 51,000 arrests.
