In an interview with The Observer published Sunday, Brown said fallout from Russia's moves to absorb South Ossetia may result in an "energy war," in which oil-producing Russia could use its vital energy supplies to its political advantage against Western Europe.

Brown vowed to avoid that, saying, "No nation can be allowed to exert an energy stranglehold over Europe." He promised urgent action to prevent Britain from "sleepwalking into an energy dependence on less stable or reliable partners."

The strong words came as Brown was preparing to attend Monday's meeting of the European heads of state called to discuss Russia's clashes with Georgia over South Ossetia. The British newspaper said the summit comes at a crucial time for Brown, who is under pressure to reverse the Labor Party's decline. He will soon unveil new measures for those dealing with the house price crash and rocketing fuel bills.

In the interview, Brown says NATO must "re-evaluate the alliance's relationship with Russia and intensify our support for Georgia and others who may face Russian aggression."