Russian President Vladimir Putin and his Iranian counterpart, Hassan Rohani, spoke via phone on January 9 about Tehran's nuclear negotiations with six world powers and the upcoming Syrian peace talks.
The Kremlin said in a statement that the leaders also discussed "current international issues."
International peace talks on the fighting in Syria, dubbed Geneva-2, are scheduled for January 22.
Iran was not on the initial invite list, despite pleas from Russia that Tehran be asked to take part.
The statement did not specify who initiated the telephone call between Putin and Rohani.
The United States this week accused Iran of helping to "brutalize" Syria.
U.S. Secretary of State John Kerry has said Iran could play a role from the "sidelines."
Based on reporting by AFP, Interfax, and ITAR-TASS