Iran vowed on Monday to keep on enriching uranium despite international demand that it freeze its controversial nuclear program, the official IRNA news agency reported.

"The request is illogical and why should Iran accept it to suspend the research activities?" said Ali Larijani, Iran's chief nuclear negotiator and head of the Supreme National Security Council.

"One should not follow such propositions... which are not rational," Larijani was quoted as saying. "Iran will follow its nuclear program with patience."

He made the remarks one day before the five permanent members of the UN Security Council -- Britain, China, France, Russia and the United States -- plus Germany are due to meet in Moscow to discuss the deadlock over Iran's nuclear issue.

The UN Security Council has demanded Iran suspend all uranium enrichment activities by the April 28 deadline, which was rejected by Tehran.

Iran, however, declared a breakthrough in making fuel for nuclear power plant last Tuesday, saying it had successfully enriched uranium to 3.5 percent purity.

Iranian President Mahmoud Ahmadinejad said a day later that his country was working on advanced P2 centrifuges -- highly efficient devices that can enrich far more effectively than the P1 technology currently in use in Iran.

"Our centrifuges are the P1 type, and the next step is the P2, which has a capacity four times greater and on which we are presently conducting research," the president was quoted as saying by IRNA.

The United Sates accuses Iran of developing nuclear weapons secretly, but Iran denied the charge, saying that its nuclear program is for fully peaceful purposes.

Source: Xinhua