Iran on Saturday denied that it planned to keep its controversial atomic programme secret, insisting the nuclear work would continue under the supervision of the UN watchdog.

"Inspections and cooperation will go on with no change or halt," Iran's representative to the International Atomic Energy Agency, Ali Asghar Soltanieh, told state radio.

"All Iranian (nuclear) activities including enrichment are under IAEA inspectors' supervision and there is no problem," he said, asked whether Iran would refrain from presenting information to the IAEA.

Iran limited cooperation with the atomic watchdog in response to a UN resolution adopted this month imposing more sanctions on Tehran for its continued refusal to halt uranium enrichment.

Soltanieh formally announced the decision in a letter sent to IAEA chief Mohamed ElBaradei on Thursday.

In a copy of the letter obtained by AFP, Soltanieh said Iran had to protect its nuclear secrets as the United States and Israel "are threatening the use of force and attack against the Islamic Republic and have repeatedly stressed that military action is an option on the table."

In 2003, Iran agreed to give immediate notification of plans to build nuclear plants or to modify existing facilities.

Now it will only notify the IAEA of new sites six months before they begin to function.

Iran says its nulcear programme is aimed at peaceful energy ends, denying allegations that it sought to secretly develop atomic weapons.