Iran says it needs new plants to supply its future nuclear power stations
The head of Iran's nuclear programme has accused the West of provoking his country into launching a plan to build 10 new uranium enrichment plants.
Ali Akbar Salehi said a UN demand for Iran to halt work on a recently revealed site had "prompted the government to approve the plan".
Iran's parliamentary speaker, Ali Larijani, said later he believed a diplomatic solution was still possible.
Tehran's move has fuelled further concerns over its nuclear programme.
Western powers say Iran is trying to develop nuclear arms. Iran says its nuclear programme is peaceful.
A source in Russia's foreign ministry told local news agencies on Monday that Russia, which supplies much of Iran's nuclear technology, was "seriously concerned by the latest statements of the Iranian leadership".
French Foreign Minister Bernard Kouchner told a French radio programme that Iran was being "a bit childish".
"Iran is playing an extremely dangerous game," he said.
"There's no coherence in all this, other than a gut reaction."
Israel's ambassador to the UK, Ron Prosor, was asked by the BBC if military action by Israel against Iran was now more likely.
He called for "all options to be on the table" without being more specific.
'We had no intention'
Iran's proposed new plants would be of a similar size to its main existing enrichment plant at Natanz.
Iran is set on processing its own uranium
Mr Salehi, who is also vice-president of Iran, said: "We had no intention of building many facilities like the Natanz site but apparently the West doesn't want to understand Iran's peaceful message."
He accused foreign powers of pushing the UN's nuclear watchdog, the International Atomic Energy Agency (IAEA), to rebuke Iran for covering up another uranium enrichment plant near the town of Qom.
"The action by 5+1 [the US, UK, France, China, Russia and Germany] at the IAEA prompted the [Iranian] government to approve a proposal to build 10 sites like that of Natanz," Mr Salehi said.
Iranian President Mahmoud Ahmadinejad told his cabinet at the weekend that parliament had ordered that Iran should produce 20,000 megawatts of nuclear energy by 2020.
It therefore needed to make 250-300 tonnes of nuclear fuel a year, he said, which would require 500,000 centrifuges for enriching uranium.
Natanz has nearly 5,000 working centrifuges, with existing plans to build 54,000 in all.
Under the plan Mr Ahmadinejad presented to the cabinet, the level of enrichment would also be increased.
The Iranian parliament reportedly later urged Mr Ahmadinejad's government to reduce co-operation with the IAEA.
Mr Larijani told reporters in Tehran that it was in foreign powers' interests to find a diplomatic solution.
"I still think there is a diplomatic opportunity and it is beneficial to them [world powers] to use this, so that Iran continues its work under the framework of the agency [the IAEA] and international supervision," he said.
While Iran maintains that it has the right to enrich uranium under the international Non-Proliferation Treaty (NPT), the parliamentary speaker questioned the value of the NPT itself.
"What is this NPT which has become a one-sided tool... to create a political atmosphere?" he asked.
"We say that we want to carry out our activities under NPT and they must guarantee this... that NPT regulations be properly applied and that they do not indulge in any political interference," the Iranian official added.