Iran on Wednesday said it will pursue "with force" the sensitive work of enriching uranium, which lies at the heart of the international community's concerns over its atomic drive.

The remarks, by Iran's nuclear chief, come ahead of a meeting Thursday in Vienna of the International Atomic Energy Agency (IAEA) over lack of progress in its efforts to verify whether Tehran's atomic activities are peaceful.

"We will continue enrichment with force," Fereydoon Abbasi Davani, head of the Iranian Atomic Energy Organisation, was quoted as saying by official Iranian media.

"Despite (international) sanctions, we have had a significant increase in the number of old and new generation centrifuges and enrichment and we will continue this development in this (Iranian) year" ending March 2013, he said.

Since 2007, Iran has been slapped by several United Nations and Western sanctions for pursuing its nuclear programme, which the international community suspects of having a military dimension -- a charge vehemently denied by Tehran.

The United Nations has passed six resolutions urging Tehran to stop enriching uranium, but Iranian officials have insisted they would pursue the process and not give in to sanctions.

Iran maintains it has a right to undertake the process as the Islamic republic is signatory to the nuclear Non-Proliferation Treaty (NPT).

The IAEA in its November report reiterated that it was "unable... to conclude that all nuclear material in Iran is in peaceful activities."

The five permanent UN Security Council members plus Germany, known as the P5+1 group and who have been negotiating in vain for the past three years with Iran, proposed last week to resume "as soon as possible" further talks with Tehran after the failure of the previous dialogue held in June in Moscow.

Tehran has not responded publicly to the proposal.

Abbasi Davani meanwhile said Iran would "soon test" its heavy water reactor which is under construction at the central town of Arak with "virtual fuel."

The IAEA noted in its report that Tehran was six months behind the earlier planned date of commissioning of the facility in the first quarter of 2014.

"Despite rumours, I say it with determination that with God's help and the effort exerted by our experts the Arak reactor is on schedule and is progressing without any problems," he said.

The nuclear chief said, without elaborating, that Iran was going ahead with caution on the reactor because of "security and safety issues since the enemy wants to inflict damage to the reactor."

"Other than that there is no technical problem," he said.

The heavy water nuclear reactor has been condemned by the Security Council and is being closely monitored by the IAEA.

The reactor does not require enriched uranium but uses plutonium which may have military applications.