Iran's nuclear negotiator Javad Vaidi made the announcement in Tehran. The talks were due to start 16 February but were postponed on 13 February.
Russia's Foreign Ministry spokesman Mihkail Kamynin said Tehran requested the four-day delay for "technical reasons."
Russia's proposal to enrich Iranian uranium is meant to allay fears that Iran is trying to develop nuclear weapons. Iran says its nuclear program is peaceful.
(IRNA, RIA Novosti, AP, Reuters)