Chief Advisor to Iranian President Mahmoud Ahmadinejad Mojtaba Samareh Hashemi denied reports on official and unofficial talks between the U.S. and Iran.
The U.S. Pugwash Research Center said U.S. and Iranian representatives met several times in 2008.
Pugwash Director Jeffrey Boutwell said four secret meetings were held between U.S. and Iranian diplomats in Austria and the Netherlands in 2008.
Hashemi said the meetings sometimes take place between non-governmental agencies and research centers. They are not held at the state level, the Iranian presidential office said in a message.
In 2008, meetings were held on the "Study of Relations Between the West and Iran" involving Iran, Russia, Canada, UK, the Netherlands and Austria.
Iran had the opportunity to explain its foreign policy to other countries.
The conference was attended by U.S. experts, heads of research centers and academics.