Georgia broke off diplomatic relations with Russia after their August 2008 war, during which Abkhazia and South Ossetia broke away from Georgia, which Russia supported, RIA Novosti reported.
"Russia has opened two embassies, in Sukhumi and Tskhinvali, and recognized the independence of Abkhazia and South Ossetia. This is the main reason diplomatic relations with Russia cannot be restored," he said.
Restoring full diplomatic ties "will be a difficult process," Ivanishvili said.
Russian President Vladimir Putin said last Wednesday he hoped to improve Russia's relations with Georgia.