Britain does not want to launch an "all-out war" with Russia following the country's decision to recognise two breakaway regions, David Miliband said.
The Foreign Secretary said Russia needed to consider the "isolation, the loss of respect and the loss of trust" from the rest of the world after Moscow officially recognised South Ossetia and Abkhazia.
Mr Miliband's comments came the day after his trip to Ukraine, where he warned Russian President Dmitry Medvedev that he had a "big responsibility" not to provoke a new Cold War.
He told BBC Radio 4's Today programme: "There is no question of launching an all-out war with Russia.
"No-one ever doubted that a Russian army of up to 800,000 people was going to defeat a Georgian army of up to 18,000 people.
"Indeed that has happened over the last two weeks. The question though for Russia is whether it wants to suffer the isolation, the loss of respect and the loss of trust that comes from that."
Mr Miliband said it was "striking" that no country had supported Russia's recognition of the two breakaway provinces.
He said he believed the only people who did were the members of militant Palestinian group Hamas.
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