"Some were saying this third step, that you want to set up modern centrifuges, means that you are moving towards a nuclear weapon," said Rouhani on state television.

"We explained that someone who wants a nuclear weapon... limits comprehensive inspections. We have not reduced inspections," he said.

Iran fired up advanced centrifuges to boost its enriched uranium stockpiles on September 7 as the latest scaling back of commitments under the crumbling 2015 nuclear deal between Tehran and world powers.

The Islamic republic acted on a threat to further abandon its nuclear commitments based on a deadline it set for European powers to act to shield it from US sanctions.

Rouhani, speaking to reporters at Tehran's Mehrabad airport on his return from the UN General Assembly, stressed all Iran's nuclear activities would continue to be monitored by the International Atomic Energy Agency.

Tensions have been escalating between Iran and the United States since May last year when President Donald Trump pulled out of the nuclear accord and began reimposing sanctions that have crippled the Iranian economy.

Britain, France and Germany have repeatedly said they are committed to saving the deal that gave Iran relief from sanctions in exchange for curbs on its nuclear programme, but their efforts have so far borne little fruit.

Tehran has already hit back twice with countermeasures in response to the US withdrawal from the nuclear deal.

On July 1, Iran said it had increased its stockpile of enriched uranium to beyond a 300-kilogramme maximum set by the deal.

A week later, it announced it had exceeded a 3.67-percent cap on the purity of its uranium stocks.