European Union observers are set to begin deploying across Georgia to monitor a ceasefire.
Two hundred monitors are expected to oversee the pullback of Russian forces from buffer zones around the breakaway regions of South Ossetia and Abkhazia.
Russia has kept troops in the zones since ousting Georgia's forces after war broke out in early August.
EU foreign policy chief Javier Solana said he was optimistic the deployment of the monitors would start as agreed.
They are due to start patrols on Wednesday, and had expected immediate access to "buffer zones" around breakaway Abkhazia and South Ossetia.
But a Russian spokesman said they would not be allowed into the zones yet.
Russia has kept troops in the zones since ousting Georgia's forces after war broke out in early August.
The EU observers from 22 nations have been deployed in Georgia to monitor Russia's troop withdrawal, which Moscow says will be completed by 10 October.
Many are French gendarmes, and there are also experts on human rights and legal issues.
But the monitors would only be able to patrol "up to the southern limit of the security zone", said Lt Col Vitaly Manushko, spokesman for Russian forces in South Ossetia, quoted by the Interfax news agency.
He said the European observers would be unarmed, and would not be able to erect observation posts.
Negotiations
The spokesman was not available to clarify his comments, and negotiations between the Russian military and the EU mission were reported to be continuing, says the BBC's Richard Galpin, in Gori, Georgia.
EU foreign policy chief Javier Solana, who was in the region to launch the mission, said: "I am optimistic that all the parties will comply, as we have done, to the terms of the agreement."
The Russian pull-back was agreed in a ceasefire deal brokered by the French President, Nicolas Sarkozy.
But Russia plans to keep nearly 8,000 troops in Abkhazia and South Ossetia, which it has recognized as independent states.
Western leaders have condemned both the buffer zones and Russia's recognition of the two regions.
The EU wants its observers to have access to the breakaway regions, but Russia has repeatedly refused to guarantee that.
Donor Conference
As the EU started to deploy its monitors to Georgia, it was confirmed that an international donors' conference would be held in Brussels next month.
The United States has pledged $1bn in aid to Georgia, and Europe is expected to match that sum when ministers from 27 EU countries gather at the conference.
The European Commission has already agreed a package worth $700m over three years to repair infrastructure and rebuild economic growth following the conflict - money which Georgia is not allowed to use to rebuild its military.
Commission officials say that Russia is unlikely to be invited to the conference, because it is unlikely to donate any money to Georgia.
EU-Russia talks
The conflict in the region began on 7 August when Georgia tried to retake South Ossetia by force after a series of lower-level clashes.
Russia launched a counter-attack and the Georgian troops were ejected from both South Ossetia and Abkhazia several days later.
A Russian defense ministry spokesman, Lt Gen Nikolai Uvarov, said Russia had removed five checkpoints in the Poti area, near the Abkhaz border.
Russia still has nine checkpoints in the zone around South Ossetia and three near Abkhazia, Russia's Ria Novosti news agency reports.
The EU observers are to be based in four field offices - in the capital Tbilisi, in Gori - just south of South Ossetia, in Zugdidi near the Abkhaz border and in the Black Sea port of Poti, Reuters news agency says.
PHOTO CAPTION
EU observers arriving in Tbilisi on, 23 September 08.
BBC