Iran's first nuclear power plant will be ready to generate electricity on April 9, atomic energy chief Ali Akbar Salehi said on Friday, in signs of yet another delay.

"We hope that on Farvardin 20 (April 9) ... we will witness the connection of the plant to the national grid," Salehi was quoted by the ISNA news agency as saying.

On November 27, Salehi announced that the plant, built by Russia in Bushehr, has begun operations, and that Tehran hoped electricity produced there would be online "in a month or two."

"The reactor has started its operation and the next step is to reach critical phase which will happen by the end of Bahman (February 20). We have said before that due to some tests, we may have face delays but these delays are around a week or two," he said on Friday.

He again reiterated that the computer worm Stuxnet had not entered the "main systems," and that Iranians are "pursing work with the Russians while observing all the safety issues."

Stuxnet has reportedly mutated and wreaked havoc on computerised industrial equipment in Iran. The New York Times has said it was tested by Israel and the United States on Tehran's atomic installations.

Salehi said "Westerners are not seeking people's health and security and will do anything to gain their aims even if it poses danger to human society.

"If anything happens to a nuclear plant its repercussions will not be confined to one border and they should know that it can tie them down," Salehi said without elaborating.

Iran says it needs the plant, which had been under construction since the 1970s, to meet growing demand for electricity.

Western governments suspect Iran's nuclear programme masks a drive for an atomic weapons capability, an ambition Tehran has steadfastly denied.