Iran will later on Monday hand over a letter to European Union foreign policy chief Javier Solana saying pressure cannot resolve the dispute over Tehran's nuclear program, Iranian media reported.
A senior Iranian official told Reuters the letter from Iran's chief nuclear negotiator Saeed Jalili and addressed to the foreign ministers of six major powers would be delivered shortly in Brussels but did not give details on its content.
"In the process of talks, pressure cannot resolve the issue," the ISNA news agency quoted Jalili as saying, giving no further information about the letter to the foreign ministers of the United States, Germany, France, Britain, China and Russia.
Iran's Press TV said in a headline: "Iran rejects any pressure on its nuclear program."
The West fears the Islamic Republic, the world's fourth-largest oil producer, is seeking to build nuclear arms.
Iran says it only wants to generate electricity and has repeatedly ruled out halting uranium enrichment, which can have both civilian and military purposes, but its refusal to do so has drawn three rounds of U.N. sanctions since 2006.
"The two-page letter reflects Iran's view over the handling of the nuclear case by the six powers. It will be handed over to Solana in Brussels in a few hours," Ahmad Khademolmelleh, a spokesman for Iran's Supreme National Security Council, said.
He told Reuters it would also be delivered to the Swiss embassy in Tehran. Switzerland represents U.S. interests in the country since Washington severed ties with Iran shortly after its 1979 Islamic revolution.
Iran's Press TV quoted Jalili as saying Iran's approach was constructive. "Iran says it has fully cooperated with the IAEA and G5+1," it said in a headline, referring to the Vienna-based nuclear watchdog and the six powers.
Jalili and Solana, representing the six powers, last discussed Tehran's nuclear program by telephone in August.
The U.N. Security Council in September passed a resolution that again ordered Tehran to halt enrichment but imposed none of the new sanctions Washington and its allies want.
Iran has dismissed the latest resolution as "unconstructive" and again made clear on Monday it would not bow to the pressure.
"There is no reason for us to change our strategy, which is not to suspend enrichment," Foreign Ministry spokesman Hassan Qashqavi told a news conference.
The six powers offered in June to hold off from seeking further sanctions if Iran freezes expansion of its nuclear work. Iran responded with a non-committal letter and Western countries said they would look at stepping up sanctions on Tehran.
But Russia and China, which gave reluctant backing to three previous sanctions resolutions that included asset freezes and travel bans on specific Iranian individuals and companies, are blocking further U.N. measures for the time being.