The EU's Luxembourg presidency reiterated its hope that negotiations with Tehran could prove successful in persuading the Islamic state to end its atomic activities definitively.

"The two sides are negotiating seriously, and as long as the Iranians continue to participate in these talks there will be a chance of success," said Luxembourg deputy foreign minister Nicolas Schmit.

"At the same time it is important to remain vigilant over the need for Iran to maintain, under surveillance by (UN nuclear inspectors), a total suspension of its activities without exception so long as the negotiations last.

He added that "a total suspension (is) the condition for the continuation and success" of the talks.

The EU commission resumed talks with Iran on a trade agreement in January, 18 months after they were suspended due to mounting concerns over Tehran's nuclear plans.

Meanwhile negotiators from Iran and the EU resumed parallel talks in Geneva Tuesday on Iran's controversial nuclear policy, amid growing pressure for progress on the issue of Iran's access to bomb-making material.

The new talks came despite Iran's continued rejection of a demand to abandon permanently uranium enrichment, a process which can assist in the functioning of nuclear power plants but also produces material for nuclear arms.

The United States maintains that Iran is trying to covertly develop nuclear weapons, while Tehran insists that its programme is purely meant to meet civilian energy needs.