"Sanctions are something not very effective," Medvedev said in a meeting with foreign experts on Russia, commenting on moves backed by some Western powers to impose further sanctions on Tehran over its nuclear programme.
"But sometimes it is necessary to use them," the Russian president stated.
Russia, which is helping the Islamic Republic construct its first nuclear plant in the southern city of Bushehr, has long resisted US-led moves to tighten the screws on Tehran through international sanctions.
The United States, the European Union and Israel fear that Iran is secretly developing nuclear weapons under the guise of its civilian nuclear power programme, but Tehran denies the charges and says the programme is peaceful.
Medvedev urged caution in moving towards further sanctions, saying this was not necessarily the best tool and arguing that further diplomatic engagement with Tehran was the best option at present.
"We should be responsible and continue discussions," he said.
