BRUSSELS - Russia could go even further in Ukraine with the "frozen conflict" strategy it has tried and tested in other countries, and may even end up annexing around half of Ukrainian territory, analysts say.
Kiev has accused Russian President Vladimir Putin of trying to "take the entire Ukraine", a scenario that several experts can picture, believing that the Kremlin is set on a military solution.
Prime Minister Arseniy Yatsenyuk said Saturday that Putin's aim was not just to annex the separatist regions of Donetsk and Lugansk but to eliminate Ukraine as an independent country.
Western countries accuse Russia of having sent more than 1,000 soldiers to fight in Ukraine alongside pro-Kremlin rebels, a charge which Moscow denies.
Since a ceasefire between Kiev and the rebels on September 5, a swathe of territory on the Russian border, from Lugansk to the Sea of Azov, remains outside Ukrainian government control.
Several analysts said Russia is already carving out a mini-state which would allow it to keep up the pressure on Kiev, as it has done in Georgia, where Moscow backed two separatist republics in the conflict there in 2008, and in Transdniestr, the Moldovan region where the Kremlin has also backed separatists.
NATO chief Anders Fogh Rasmussen said Monday that the "long-term ambition of Russia is to establish a zone of influence in its near neighbourhood" and stop bordering countries from joining alliances such as the EU or NATO.
And some analysts believe Putin - who has taken to using the tsarist-era term Novorossiya, or New Russia, to describe parts of Ukraine - has ambitions that go much further still.
"How far Russia will go in southern Ukraine depends mainly on calculations in the Kremlin: How many casualties are acceptable? How much damage to relations with the West can be sustained?" said Ulrich Speck, a visiting scholar at the Carnegie Europe think-tank in Brussels.
"And can territory that has been conquered actually be administered under Russian control, or will it be subject to an endless partisan war?"
Researchers from the Warsaw-based Polish Institute of International Affairs expect Ukraine's pro-Russian rebels to mount a new offensive against government forces this winter and have been war-gaming the most likely scenarios.
The most probable outcome, they say, is Russian intervention in late October to ensure a land corridor 300 kilometres long and 50 kilometres wide (180 miles long by 30 miles wide) to guarantee energy and food supplies for Russian-annexed Crimea.
A second scenario that is "30 per cent likely" is that Russia could proclaim the creation of "Novorossiya" in the southern half of Ukraine, supported by 50,000 to 70,000 Russian soldiers, and linking Moldova's Transdniestr to Crimea, they say.
The Ukranian economy would be devastated by any such move, which would cost the country seven seaports including Odessa as well as two nuclear power stations, with an estimated loss of 27 per cent of gross domestic product (GDP).
Around one million people live in the region in question.
The gloomiest scenario involves a complete partition of the country with 100,000 Russian troops controlling the industrial east.
"All of these are realistic. It depends on the timescales," Giles Keir of the Chatham House think-tank in London told AFP.
The Royal United Services Institute, a British military think-tank, has long warned of similar scenarios, saying that Russia's huge arms industry depends on Ukraine for 30 per cent of its essential components, particularly for aircraft and missiles, which might tempt Moscow to intervene.
Keir said Putin held the advantage because of his "strategic patience" - largely because Western democracies must worry more about domestic political cycles.
"Russia does things while people are looking away," for example the invasion of Georgia during the 2008 Beijing Olympics, he said.
"The initiative is entirely in their hands."