An influential Iranian cleric said Sunday that the West must know Iran's nuclear program is " irreversible," the state-run IRNA news agency reported.

Akbar Hashemi Rafsanjani, Chairman of Iran's Assembly of Experts and Chairman of the Expediency Council, said that "they (the West) must know that Iran is very serious about its nuclear program, both on enrichment and uranium swap, and our way is irreversible."

Tehran rejected a Dec. 31 deadline set by the United States for Iran to accept a UN-drafted deal for swapping its low-enriched uranium for nuclear fuel outside Iran, and instead demanded a simultaneous exchange inside the country.

On Jan. 2, Iran set a one-month deadline for the West to accept its counterproposal to the UN-drafted nuclear plan and warned that otherwise it will produce fuel for Tehran research reactor at a higher level of enrichment on its own.

Western countries have accused Iran of covertly building nuclear weapons but Tehran maintains that its nuclear program is peaceful and intended to generate electricity for civilian use.