Internationally backed talks to resolve Russia-Georgia tensions following last year's war collapsed Monday in acrimony as the Russian side walked out and the Georgians accused them of blackmail.
The Russians abandoned the Geneva meeting after complaining about the absence of the delegation from the Georgian breakaway region of Abkhazia, which boycotted the event, a diplomatic source told AFP.
"The Russians left in the middle of the talks along with the Ossetians," the source said, referring to another separatist Georgian region, South Ossetia, which was at the centre of last August's conflict.
"They felt there was no reason to discuss security in the Caucasus without the Abkhazians," the source added.
In Moscow, Russian Foreign Minister Sergei Lavrov said his delegation had decided to "take a pause" until Tuesday.
"The basic conditions required to guarantee this round of talks were not respected," he told Russian news agencies.
Mediators said they would try to resume the two-day meeting on Tuesday.
Georgia's Deputy Foreign Minister Giga Bokeria reacted angrily to the walk-out, accusing Russia of trying to "blackmail the international community.
"This shameful step is yet another violation of the European Union-brokered ceasefire agreements and of the latest UN resolution," he told AFP.
The United States said it was "dismayed" at the walkout.
"The fact that the walkout occurred before any substantive discussions began clearly signals a coordinated effort to undermine the Geneva talks," State Department spokesman Ian Kelly told reporters in Washington.
The meeting was the latest in a series of talks that began in October 2008 under the joint auspices of the United Nations, the European Union and the Organization for Security and Co-operation in Europe (OSCE).
The mediators issued a joint statement saying they "strongly regret the walk-out" by the Russian and South Ossetian delegations.
"The co-chairs are working for the resumption of the discussions tomorrow morning, 19 May, as planned and call upon all participants to be present," the EU, the UN and the OSCE added.
France also urged talks to resume.
"We call on all parties (to resume) from May 19 their participation in the international discussions in Geneva, which are an essential element for the stabilisation of the region and resolving humanitarian questions," the French foreign ministry said in a statement.
Diplomats said earlier they hoped Abkhazian officials might still participate in Tuesday's second and final day on talks. This now looks unlikely.
Abkhazia had threatened on Saturday to boycott the discussions in protest at how the United Nations had described the region's status. They made good on that threat by failing to turn up when the talks began.
In UN reports the region is referred to as Abkhazia, Georgia. This infuriates representatives of the Moscow-backed region since it implies the separatist-minded territory is part of Georgia.
A new UN report was due out in New York late Monday and Lavrov said he was waiting to see its contents.
The rebel regions of Abkhazia and South Ossetia are regarded by Russia as independent states but most of the world still recognises them as part of Georgia.
Diplomats had expected things to be rocky at the Geneva talks because of several events in recent weeks which underscored the lingering tensions in the region.
Earlier this month the Georgians accused Russia of encouraging a mutiny by army officers at a barracks near the capital Tbilisi on the eve of NATO military exercises.
Also, a security meeting between Georgian, Russian and South Ossetian officials was called off on May 7 because of disagreements about where it would be held. Tbilisi and Moscow blamed each other for the cancellation.
At the last round of talks in Geneva in February, Russia and Georgia took the first concrete steps to preventing new clashes by accepting proposals to open up more immediate channels of military communication.
But several other security problems, including key issues relating to militia movements and force build-ups, remain unresolved.
Other outstanding issues include finding an agreement on providing humanitarian aid to Georgian populations in South Ossetia and the return of refugees.
Russian troops and tanks poured into Georgia in early August 2008 to repel a Georgian assault on the breakaway region of South Ossetia, which had received extensive backing from Moscow for years.
Russian forces occupied swathes of the country, but later withdrew to within South Ossetia and another rebel region, Abkhazia, which Moscow simultaneously recognised as independent states.