On Monday, the European Commission in Brussels announced it would give $700m in aid over two years to help Georgia rebuild infrastructure destroyed in the fighting.
The secretary-general was met at the steps of his plane by Georgian officials and an honour guard of soldiers with Georgian flags flying from their bayonets.
As the ambassadors arrived in Tbilisi, Dmitry Medvedev, Russia's president, warned the West that any sanctions imposed on Moscow over the war in Georgia would backfire.
"It's senseless to pressure Russia with sanctions,'' Medvedev said at a meeting with Russian business leaders.
"They can shut a couple of sources of [revenue] to a banana republic and make its situation dramatic. It won't work like that here.''
Without mentioning any specific nation, Medvedev warned that attempts to punish Russia would also hurt the West.
"Sanctions is a weapon that will backfire,'' he said. "If attempts are made to introduce sanctions, damages will be symmetrical.''
The president also dismissed calls by some Western diplomats to prevent Russia from joining the World Trade Organisation (WTO).
Russia would like to join the WTO but would not be pressured into concessions, Medvedev said.
"The WTO isn't a carrot, it entails a lot of difficult obligations,'' he said. "And if we do it, let us do it in a normal way without them trying to scare us.''
Last month's Russian military push into Georgia to repel a Georgian attack on South Ossetia has been condemned by the alliance, as has Moscow's subsequent recognition of South Ossetia and another breakaway region, Abkhazia, as independent.
Under an European Union-backed deal all Russian troops will leave uncontested parts of Georgia by the middle of next month, while 7,600 Russian soldiers, more than twice the pre-war levels, will remain in South Ossetia and Abkhazia.
In an interview published on Monday in London's Financial Times newspaper, de Hoop Scheffer said the EU agreement to help end the conflict had been "difficult to swallow" because it made too many concessions to Russia.
"If the Russians are staying in South Ossetia with so many forces, I do not consider this as a return to the status quo," de Hoop Scheffer said.
"The option of keeping Russian forces in South Ossetia and Abkhazia is not acceptable."