Iran's influential former President, Akbar Hashemi Rafsanjani, has lashed out at the international community's anger at Iran's nuclear research.
Mr Rafsanjani said the West's reaction was arrogant and colonial
He said he was "astonished" by the "bullying, particularly in the era of democracy, freedom and human rights".
Top European foreign ministers are to meet on Thursday to consider their response to Iran's resuming research.
The West fears Iran is seeking nuclear weapons - a charge it denies - after it broke seals on a research facility.
British Foreign Secretary Jack Straw has expressed his "profound concern" and said taking the matter to the UN Security Council was on the agenda for Thursday's meeting.
"We'll make a decision then ... but I think it's clear the direction in which we're thinking," Mr Straw said.
Mr Rafsanjani, preaching special prayers to mark the end of the hajj pilgrimage, said the "colonial" West was seeking to keep the rest of the world ignorant.
"This is tantamount to arrogance and discrimination," he said in remarks broadcast live on state television.
On Tuesday, Iran removed UN seals from equipment at Natanz facility. The UN nuclear watchdog, the International Atomic Energy Agency (IAEA), said Tehran would start small-scale nuclear enrichment.
The move was condemned by the US and European countries.
IRAN'S NUCLEAR STANDOFF
Sept 2002: Work begins on Iran's first nuclear reactor at Bushehr
Dec 2002: Satellite photographs reveal nuclear sites at Arak and Natanz; Iran agrees to an IAEA inspection
Sept 2003: IAEA gives Iran weeks to prove it is not pursuing atomic weapons
Nov 2003: Iran suspends uranium enrichment and allows tougher inspections; IAEA says no proof of any weapons programme
June 2004: IAEA rebukes Iran for not fully co-operating with nuclear inquiry
Nov 2004: Iran suspends uranium enrichment as part of deal with EU
Aug 2005: Iran rejects EU proposals and resumes work at Isfahan plant
Jan 2006: Iran removes seals at Natanz facility
"This is a matter which has to be resolved by peaceful means, but it will involve a good deal of diplomatic and other pressure on Iran," Mr Straw said.
He confirmed he would meet French Foreign Minister Philippe Douste-Blazy, Frank-Walter Steinmeier of Germany and Javier Solana, the EU foreign policy chief, on Thursday.
The EU meeting could trigger an emergency meeting of the IAEA's board of governors - probably in two to three weeks' time.
The board could then refer the matter to the UN Security Council in New York.
At the Security Council there are still many options, ranging from a statement endorsing the IAEA's efforts to full-scale sanctions.
The likelihood is that action, if any, will be towards the less dramatic end of the scale, reports the BBC's diplomatic correspondent Jonathan Marcus.
White House spokesman Scott McClellan said Iran was risking a "serious escalation" in the dispute, adding the international community would have no other choice but to refer Tehran to the UN.
Russian Foreign Minister Sergei Lavrov said his country was taking "active measures together with the Iranian side in order to keep this [Iranian] moratorium effective".
Although the Iranian enrichment experiments are small-scale and just for research purposes, there are fears they could lead to Iranian scientists mastering uranium enrichment, correspondents say.
Depending on the level of enrichment, the uranium enrichment process results in either nuclear fuel or weapons grade uranium for nuclear warheads.