"The supplies of Russia’s S-300 air defense system to Iran is due soon," he told the media following talks with his Iranian counterpart Javad Zarif on Thursday.
Zarif is in Moscow to attend the Shanghai Cooperation Organization (SCO) Council of Ministers of Foreign Affairs meeting and the High-level Conference "Security and Stability in the SCO Region".
According to TASS news agency, Lavrov said that the theme of S-300 systems was not discussed during the meeting.
"We merely stated that preparations for the delivery are underway and the deal will be effected soon," he said.
Russian President Vladimir Putin decided in April to lift a ban on the S-300 missile system delivery to Iran. The ban had been introduced by former Russian president Dmitry Medvedev in 2010.
Under a contract signed in 2007, Russia was required to provide Iran with at least five S-300 defense system batteries.
In 2010, Medvedev cancelled the contract as he came under strong US and Israeli pressure not to go ahead with the sale of the weapons system, but his pretext was that the sale was covered by the fourth round of the UN Security Council sanctions against Iran.
Iran had filed a $4 billion lawsuit against Russia in an international arbitration court in Geneva in April 2011 after Russia suspended the 2007 contract.