Medvedev's comments came a day before EU leaders meet to draft a response to Moscow's actions in Georgia.
European leaders are divided as to how to respond to Russia decision to recognise Georgia's breakaway regions as independent states and to send troops into Georgia after Tbilisi attacked South Ossetia in August.
Gordon Brown, the British prime minister, said he would press EU leaders to review their ties with Russia.
Frank-Walter Steinmeier, the German foreign minister, took a softer line, saying isolating Russia would harm the interests of the bloc.
A senior US diplomat said Washington hoped the EU would express concrete support for Georgia's territorial integrity, and urged Europe to reduce its dependence on Russian energy.
Chris Weafer, the chief strategist with Russia's Uralsib investment bank, said the meeting is likely to produce a "stern words-soft action" response.
The bloc is likely to "stop well short of any action that might escalate into a damaging tit-for-tat sequence of economic and political sanctions," Weafer wrote in a research note.
Georgia called on the EU to impose sanctions against those doing business with its separatist regions and for a civilian mission to be sent to monitor buffer zones inside the country.
|South Ossetia, part of Georgia, has been long been backed by Moscow [AFP]
Tbilisi also wants about $2bn to help repair damage caused in the recent conflict.
"Europe can do a lot, starting with sending a mission of civilian monitors, which would lead to an international peacekeeping mechanism that would replace the presence of Russian troops," Lado Gurgenidze, Georgia's prime minister, said.
Mikheil Saakashvili, the Georgian president, said that he expected Europe to come out in support of Georgia at the summit.
"I expect that Europe will support our territorial integrity and will say that it will never recognise these illegal actions," he said in an address to the nation, according to his website.
"I do not know for sure what will happen in Brussels tomorrow, but I know that it is the beginning of major process."
Saakashvili said that "Russia today is more isolated than it ever was during the existence of the Soviet Union" and called on Georgians to turn out en masse for rallies across Georgia on Monday.
Tens of thousands of people are expected to take part in the rallies and form a human chain running through the Georgian capital Tbilisi, as well as in major Georgian and European cities.