From L to R, Veronique De Keyser, a member of Belgiums's Socialist party, Hannes Swoboda of the Austrian socialist and democratic party and Portuguese politician Ana Gomes, in Tehran on October 20, 2013

Accompanied by Ana Gomes and Veronique de Keyser, he made the remarks in a meeting with Iranian parliament speaker Ali Larijani, the ISNA news agency reported.

Iran and EU nations could once again become "trustworthy partners" if "both sides take advantage of the current situation and take steps towards a final agreement" to resolve the nuclear issue, Swoboda said.

The unofficial visit comes amid raised hopes of Iran constructively engaging the international community following the election of President Hassan Rouhani, a moderate who has pledged a new approach to the talks.

Rouhani, who took office in August, has promised more transparency on Iran's nuclear drive, which the West suspects is aimed at military objectives despite repeated Iranian denials.

Larijani, the conservative speaker of Iran's parliament, expressed support for negotiations between Iran and the P5+1 -- the United States, Britain, France, Russia, China and Germany.

"These negotiations could achieve constructive results if conducted in a just and logical framework, and if previous excuses are overlooked," he said without elaborating.

Iran is hoping the talks revived in Geneva last week will lead to the lifting of harsh international sanctions that have damaged its economy.