Russia says the first delivery of its S-300 missile-defense system to Iran will take place in August or September this year.
The comment on March 11 by Sergei Chemezov, the head of Russia's industrial conglomerate Rostec, comes amid reports the deal has run into difficulties.
Unidentified Russian officials told the Kommersant newspaper on March 9 that problems with payment issues had arisen.
The Russian daily said the contract, sealed last November, requires Iran to pay some $1 billion in several installments and anticipated the first delivery to be made in February.
The report in Kommersant came after a Kuwaiti daily quoted a high-level source as saying Moscow had decided to suspend shipments.
Both Kremlin spokesman Dmitry Peskov, and a spokesperson for Russian arms exporter Rosoboroneksport declined to comment on the Kuwaiti report, Kommersant reported.
Israel and the United States fear the missiles could be used to protect Iranian nuclear sites from air strikes.
Based on reporting by The Moscow Times and Reuters