Foreign Secretary David Miliband will visit Ukraine later in an attempt to build the "widest possible coalition against Russian aggression".
The trip comes after Russian President Dmitry Medvedev declared he formally recognised Georgia's breakaway regions, reported BBC.
Mr Miliband has branded the move "unjustifiable and unacceptable".
Ukraine's president Victor Yushchenko has described his country as a hostage in a war being waged by Russia against states in the former Soviet bloc.
And he said the brief war between Georgia and Russia had exposed serious weaknesses in the powers of the UN and other international bodies.
Fighting between Russia and Georgia began on 7 August after the Georgian military tried to retake South Ossetia by force.
Russian forces subsequently launched a counter-attack and the conflict ended with the ejection of Georgian troops from both South Ossetia and Abkhazia - which already had de facto independence - and an EU-brokered ceasefire.
He said Russia's recognition of the breakaway regions "further inflames an already tense situation".
"It takes no account of the views of the hundreds of thousands of Georgians and others who have been forced to abandon their homes in the two territories," he said.
"We fully support Georgia's independence and territorial integrity, which cannot be changed by decree from Moscow."
Moscow's move has been criticised by other world leaders.
France, the current holder of the presidency of the European Union, called for a political solution.
French Foreign Minister Bernard Kouchner said: "We think it is against the territorial integrity of Georgia and we cannot accept it."
Nato said it was a "direct violation" of UN resolutions, and US President George Bush warned his Russian counterpart that his "irresponsible decision" was exacerbating tensions in the region.
Mr Bush called on Russia to reconsider and "live up to its international commitments".
But Mr Medvedev said the West would have to "understand the reason behind" the decision if it wanted to preserve good relations with Russia.
He said Russia had been obliged to act following the "genocide" started by Georgian President Mikhail Saakashvili in South Ossetia in August.
"The most important thing was to prevent a humanitarian catastrophe to save the lives of people for whom we are responsible, because most of them they are Russian citizens," he told the BBC's Bridget Kendall in an exclusive interview in the Russian town of Sochi.
"So we had to take a decision recognising the two states as independent."
He said a new Cold War could not be ruled out, but that his country did not want one.
"There are no winners in a Cold War," he said.
Georgia said Russia was seeking to "change Europe's borders by force".
Most of Russia's forces pulled out of the rest of Georgia last Friday but it maintains a presence both within the two rebel regions and in buffer zones imposed round their boundaries.
Mr Medvedev has blamed Georgia for failing to negotiate a peaceful settlement to the crisis.