While Iran cited the fourth round of nuclear talks with the United States as "difficult but useful", President Masoud Pezeshkian stressed that any speculation about discarding Iran's entire nuclear infrastructure is completely unacceptable because the country has the right to use nuclear energy for civilian purposes and is not seeking a nuclear weapon.

"Iran will not relinquish its peaceful nuclear rights," Pezeshkian told a cabinet meeting on Sunday. He said US calls to dismantle Iran's nuclear infrastructure are "unacceptable" and reaffirmed the stance that Iran's nuclear program is for civilian purposes only.

He also cited a religious fatwa issued by Iranian Supreme Leader Ali Khamenei, which completely prohibits building weapons through the development of nuclear energy. The fatwa was first announced in 2003 and an official statement was released at a meeting of the International Atomic Energy Agency in Vienna in 2005.

Pezeshkian said the advancements made by Iranian scientists in the peaceful nuclear sector have applications in various fields including agriculture, environmental protection, industry and medicine, the Islamic Republic News Agency reported.

"The Islamic Republic does not seek unrest in the region by any means," Mehr News Agency quoted Pezeshkian as saying. "We can assure you that the Islamic Republic of Iran has never sought, is not seeking, nor will seek nuclear weapons."

Facilitated by Oman, the US and Iran held the fourth round of indirect talks in Muscat on Sunday, the latest attempt to revive the Joint Comprehensive Plan of Action. The US unilaterally abandoned the nuclear deal in 2018 during President Donald Trump's first term. Oman has yet to release a new date for the next round of talks.

Iran's Foreign Minister Abbas Araghchi said in Muscat on Sunday that the talks were "much more serious and frank", with the two sides now having a "better understanding" of each other's positions.

This round of talks moved beyond broad discussions and delved into specifics, making the negotiations more challenging as they move forward, he said.

The Iranian Foreign Ministry said negotiators from both sides engaged in "difficult but useful talks to better understand each other's positions and to find reasonable and realistic ways to address the differences".

Uranium enrichment

US officials indicated that Washington was "encouraged" by the talks with Iran but key questions remain, including whether Teheran will be allowed to enrich its own uranium.

The indirect discussions focused on Iran's nuclear program and the lifting of sanctions, also key points of contention between the two countries. The discussions remain challenging because of hardened US positions on Iran's peaceful nuclear activities.

Ahead of the talks, US Secretary of State Marco Rubio said Iran has to "walk away" from uranium enrichment and long-range missile development, and it should allow the US to inspect its facilities.

In response, Araghchi stressed that enriching uranium, a key component of any nuclear program, remains "nonnegotiable" for Iran.

Israeli Foreign Minister Gideon Saar said on Sunday that Iran's uranium enrichment facilities "must be dismantled" and that the US and Israel agree on this issue, The Times of Israel reported.

Xinhua and agencies contributed to this story.