Iran said on Tuesday it views its nuclear activities as a non-negotiable right, but confirmed they will be discussed in mooted talks with world powers.

"The issue of our country's peaceful nuclear activities will be on the agenda of talks between Iran and the P5+1 (the five permanent UN Security Council members plus Germany)," foreign ministry spokesman Ramin Mehmanparast told reporters in a televised briefing.

"Our main demand is recognition of our right to possess the (nuclear) technology for peaceful purposes," Mehmanparast said.

"That right has been achieved, and we don't think there is a negotiable issue regarding our nuclear activities."

Mehmanparast's comments came on the second day of a two-day visit by officials from the UN nuclear watchdog for talks focused on "possible military dimensions" of the nuclear programme.

The visit was seen as an important precursor to the possible P5+1 talks.

The ministry spokesman said the aim of the visit by the International Atomic Energy Agency officials was not inspections but to talk about "a framework to pursue dialogue and cooperation between Iran and the IAEA."

A previous IAEA visit to Tehran late last month was inconclusive.

Meanwhile, the European Union was studying Iran's positive response to an offer it made late last year to revive talks with the P5+1 that collapsed in January 2011.

EU foreign policy chief Catherine Ashton said the talks could resume if Iran placed no pre-conditions on them, particularly concerning its nuclear programme.

In the more than three months it took Iran to reply to Ashton's offer of renewed talks, Tehran has forged ahead with its nuclear activities, declaring it was adding thousands more centrifuges to its uranium enrichment activities and producing what it said was 20-percent enriched nuclear fuel.

"These have been really major achievements," Foreign Minister Ali Akbar Salehi said on Tuesday, during a joint news conference with his Omani counterpart.

He said Western nations had initially been skeptical of Iran's ability to make the nuclear fuel, but "now we have succeeded they have changed their tone," as presented in Western media.

The UN nuclear agency in November issued a report voicing strong suspicions that Iran was engaged in research for an atomic weapon and ballistic missile warhead design.

Iran is also battling with the economic pressure from Western sanctions.

On Monday, it said it could expand a halt on oil exports to the European Union, following a stoppage announced at the weekend to France and Britain, in apparent retaliation for an EU oil embargo due come into full effect in July.

The European Union, though, said it could cope with any halt in Iranian supplies.

"The EU is well stocked with oil and petroleum products to face a potential disruption of supplies," said a spokesman for Ashton.

In Rome, French Foreign Minister Alain Juppe dismissed Tehran's move.

"Undoubtedly, Iran is very imaginative with regards to provocation. It is not Iran that decided to cut off its deliveries, we are the ones who decided to terminate our orders," he told reporters.

"People are actually calming down after realising that this is a game of political brinksmanship from Iran," said one analyst, Justin Harper, head of research at IG Markets Singapore.