Iran's nuclear negotiator Said Jalili sent a protest to EU foreign policy chief Javier Solana on Monday over the West's attitude to his country's atomic programme, a senior Iranian official said.
"In the letter, Mr Jalili complains of the attitude of the West and says their approach has harmed the constructive process of negotiations between the two parties," the official told AFP, declining to be named.
"In the course of negotiations, pressure instead of reason will not be a resolution," the official news agency IRNA cited the two-page letter as saying.
The office of Iran's Supreme National Security Council said the letter was delivered to Solana on Monday by the Islamic republic's ambassador to Brussels, Ali Asghar Khaji. Copies of the letter are due to go to the foreign ministers of the five UN Security Council permanent members - Britain, China, France, Russia and United States - plus Germany.
Western countries hit out at Iran at a meeting in Vienna last month over its refusal to disprove allegations of past nuclear weapons work and for pursuing uranium enrichment in defiance of UN demands.
The International Atomic Energy Agency's latest report on its six-year probe into Tehran's contested nuclear drive "presents a decidedly bleak picture," German ambassador Ruediger Luedeking told the IAEA's 35-member board. "Iran continues to defy the requests of the international community," Luedeking said, speaking on behalf of the so-called EU-3 of France, Germany and Britain. The UN Security Council has slapped three rounds of sanctions on Iran for refusing to suspend uranium enrichment, a process which can be used to make the fissile material for a nuclear bomb.