Hashemi-Rafsanjani, who lost to President Mahmud Ahmadinejad in a runoff election in June and heads Iran's top political arbitration body, the Expediency Council, called on Western nations not to do anything they would later regret.
"The West should now act wisely and not do anything which they themselves would later regret," Hashemi-Rafsanjani said, according to dpa.
Western and Russian leaders have condemned Iran for its decision on 9 January to renew work on nuclear fuel.
The United States has called Iran's latest move a "serious escalation." White House spokesman Scott McClellan told reporters on 10 January that Iran risks an situation that could end in UN Security Council sanctions.
"If Iran continues on this path and we realize that the negotiations have run their course, I think the international community is prepared to move to the next step," McClellan said.
European Union countries are now debating whether to continue negotiations to persuade Iran to abandon its nuclear ambitions.
U.S. military and other officials suspect Iran is seeking to develop nuclear weapons, while Iranian officials counter that the country's nuclear program is for peaceful purposes only.
(compiled from news agency reports)
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