Delivering Iran's first reply to the chorus of protests, Rafsanjani, who heads the powerful Expediency Council, said he was "astonished" by the West's attempt to "bully" Iran.
In London, Prime Minister Tony Blair indicated Britain would push for the U.N. nuclear body, the International Atomic Energy Agency, to refer Iran to the U.N. Security Council, which could impose sanctions.
"I think the first thing to do is to secure agreement for a reference to the Security Council, if that is indeed what the allies jointly decide, as I think seems likely," Blair told parliament.
White House press secretary Scott McClellan said Tuesday that Iran's course left "no other choice but to refer the matter to the Security Council."
Asked about sanctions, Blair said: "We obviously don't rule out any measures at all."
In Moscow, the Foreign Ministry said Russian Foreign Minister Sergey Lavrov had discussed the issue with U.S. Secretary of State Condoleezza Rice and both sides shared "a deep disappointment" over Iran's move.
France, Germany and Britain are due to meet at ministerial level Thursday to discuss their response to Iran. The three nations have been negotiating with Tehran for two years in a bid to ensure its nuclear program is peaceful.
"I don't know what the three foreign ministers will decide tomorrow, but I believe they cannot continue to negotiate without an Iranian assurance that there will be no concrete enrichment activity," said German Deputy Foreign Minister Gernot Erler.
The three European powers had been scheduled to resume talks with Iran on Jan. 18.