Ahmadinejad said Medvedev entered a U.S. "propaganda war" against Iran by saying last week that Iran was nearing nuclear weapons capability.
Here's what semiofficial ISNA news agency quoted Ahmadinejad as saying:
"The Russian and Iranian nations are friends and we're interested in continuing this friendship, but Medvedev's comments were the trailer of a play that the U.S. wants to carry out against Iran. This play was written and is being directed by the U.S. Unfortunately out of ignorance or because of wrong analysis, some are playing in this drama against their interests. The question is why the Russian president is playing in this American drama?"
Ahmadinejad added that he would unveil more details about the scenario and its main players. "Thank God we have access to this scenario, even though they think it is secret," he added.
Russia has been a traditional ally of Iran, in which it has long-term economic interests.
But Moscow angered Tehran last month when it supported the latest UN sanctions resolution against the Islamic republic over its refusal to halt sensitive nuclear work.
Ahmadinejad first publicly criticized Russia in May when it became apparent that Moscow would support new sanctions against Iran, saying that interpreting Russia's behavior "has become more and more difficult" for Iran.
Last month, an Iranian lawmaker said that Iran's Intelligence Ministry had called for a "decrease" in ties with Russia.
-- Golnaz Esfandiari