Medvedev's decision Tuesday to recognize the Georgian breakaway provinces South Ossetia and Abkhazia as independent drew condemnation from the West. Though no other countries have followed Russia's lead, Medvedev reaffirmed the decision on Sunday.
"We have made our decision, and it's irreversible," he said in a speech broadcast on Russian television.
The war began Aug. 7 when Georgian forces began heavy shelling of the South Ossetian capital, Tskhinvali, hoping to retake control of the province. Russian forces poured in, pushed the Georgians out in a matter of days and then drove deep into Georgia proper.
European Union leaders planned an emergency meeting Monday to discuss how to deal with an increasingly assertive Russia, but they are not expected to impose sanctions. Russian Prime Minister Vladimir Putin has angrily warned Europe not to do America's bidding and said Moscow does not fear Western sanctions.
Medvedev said Sunday the world would be more stable if the U.S. was less dominant.
"The world must be multi-polar; domination is unacceptable," he said. "We can't accept the world order where all decisions are made by one nation, even by such serious and authoritative nation as the United States. Such a world would be unstable and prone to conflicts."
Still he insisted Russia does not want to distance itself too much from the West.
"Russia doesn't want to isolate itself," he said.
Georgian President Mikhail Saakashvili said the EU summit was a sign of a strong global support for Georgia.
"Russia today has found itself more isolated than the Soviet Union ever was," he said in a televised statement.
Georgia asked the EU and the U.S. to impose sanctions on companies and individuals that do business in Abkhazia and South Ossetia without its permission.
Medvedev said Russia was preparing to sign deals with the two provinces that will detail Moscow's obligations on economic, military and other assistance to them. He said the agreements will lay the foundation for "allied" relations.
"We will provide all kinds of assistance to these republics," Medvedev said. "These international agreements will spell out our obligations on providing support and assistance: economic, social, humanitarian and military."
Medvedev also said Russia will protect what he called its "privileged" interests in the former Soviet nations and defend its citizens and the interests of its businessmen abroad. He said Russia may consider economic sanctions against unfriendly nations, but would like to avoid it.
Medvedev's predecessor and mentor Putin cautioned European nations against adopting the tough U.S. stance on Russia and "serving someone else's political interests." Speaking to Russian television Sunday, Putin voiced hope that the Europeans will "look out for their own skins."
Putin, who was speaking during a visit to Russia's far eastern region, said Russia will diversify its energy exports and expand sales to booming Asian markets. His comments appeared to be a response to British Prime Minister Gordon Brown's call in an article published Sunday for Europe to adopt a united energy policy and avoid dependence on Russia.
Russia supplies the EU with about a third of its oil and about two-fifths of its natural gas, and can turn off the tap if it chooses.
Putin said, however, that Russia's plans to expand energy exports to Asia doesn't mean that it would cut supplies to European markets.
"We aren't going to impose any restrictions. We will fulfill our contract obligations," Putin said. "But we will expand and diversify our opportunities in exporting hydrocarbons. The global economy, and, particularly, the rapidly growing Pacific region, need that." Georgia has severed diplomatic ties with Moscow to protest the presence of Russian troops on its territory. It claims, as does the West, that Russia is violating an EU-brokered cease-fire mandating that both sides return their forces to prewar positions. Russia has interpreted one of the agreement's clauses as allowing them to remain in security zones, now marked by Russian checkpoints.
Georgia appears likely to be hosting tens of thousands of refugees for a grindingly long and expensive time. How much aid the small and struggling country will need to support them is to be among the top issues of the EU summit on Monday.
The United States has sent substantial aid to Georgia following the war, using naval ships and military aircraft. Russian officials speculated that the United States was trying to restore Georgia's armed forces, which had received massive military aid from Washington in recent years.
AP correspondents Jim Heintz in Karaleti, Georgia, Vakho Zabashta in Gori, Georgia, and Misha Dzhindzhikhashvili in Tbilisi, Georgia contributed to this report.