FACTBOX: Scenarios for Russia-Ukraine gas row

(Reuters) - A conflict between Russia and Ukraine over their gas contract has choked supplies of the fuel to countries across the European Union, leaving some people struggling to heat their homes in freezing winter temperatures.

Here are some scenarios of what may happen next:

A COMPREHENSIVE DEAL

Under pressure from a European Union increasingly worried about its gas supplies, Russian gas export monopoly Gazprom and Ukrainian state energy firm reach a comprehensive agreement. That would mean resolving a dispute over how much Ukraine should pay for its gas, and how much Russia pays for shipping fuel to Europe across Ukrainian territory.

If such a deal was struck, gas supplies from Russia for Ukraine's domestic use would be restored, and -- more importantly for Europe -- the transit of gas to EU customers could also start again. It would not be an instant remedy because the distances involved mean it would take more than 24 hours for the gas to start flowing normally again.

A PARTIAL DEAL

Under this scenario, Russia and Ukraine would agree to resume gas flows to Europe while leaving their own dispute on hold until a later resolution. Monitors the European Union is planning to send to pumping stations along the pipeline routes would help reassure Moscow that Kiev is not siphoning off gas intended for Europe. In the meantime, Gazprom would keep the gas taps to Ukraine itself closed, leaving it with some leverage over Kiev in their dispute. A final resolution would not be quick: Ukraine says it has enough gas stockpiled to last until the winter is over. Another stumbling block in talks between Moscow and Kiev could be the future of gas trader RosUkrEnergo, which Kiev wants to scrap as the monopoly importer of Russian gas to Ukraine.

NO DEAL AT ALL

If the dispute drags on into next week with gas flows via Ukraine still halted, European Union economies will start to feel real pain. The energy restrictions and factory shutdowns already seen in countries like Bulgaria could spread West and North into the EU's industrial heartlands. Countries like Germany, the continent's biggest economy, have large gas stockpiles and alternative sources of gas. But the longer the gas switch-off goes on, the more problems they will face, especially if there is no let-up in freezing temperatures.

RUSSIA GETS TOUGH WITH UKRAINE

And the longer the dispute drags on, the more Russia will be inclined to take tougher action against Ukraine, the country it holds responsible for holding it and energy customers in Europe to ransom. Should Russia decide to go down this path, its response could take a number of forms:

* DIPLOMATIC CAMPAIGN: Russia could use its weight as a permanent member of the United Nations Security Council to seek a resolution condemning Ukraine's actions. Russian diplomats could also lobby the European Union to punish Ukraine, perhaps by cancelling some of the joint programs Kiev sees as a stepping stone to eventual EU membership.

* ECONOMIC SANCTIONS: Restricting the movement of people, capital and goods across the border with Russia and Ukraine would have a crippling effect on Ukraine, which exported $15 billion worth of goods to Russia this year.

Russian President Dmitry Medvedev already threatened Ukraine with sanctions in December.

Before their war last year, Russia imposed a partial economic blockade on Georgia. It closed their land borders, halted direct flights and banned wine and mineral water, major Georgian exports, from Russian markets.

* MILITARY ACTION: This would be a last resort and no official in Russia has mentioned this as an option. There have been no indications that anyone in Russia is even considering it. But Medvedev has made clear Russia reserves the right to use military action in certain cases.

"Russia's interests must be secured by all means available, this is my deep conviction. First of all, by international and legal tools ... but, when necessary, by using an element of force," Medvedev said in a television interview in December.

Russia demonstrated these were not empty words last August, when it launched a massive offensive on Georgia after Tbilisi's forces tried to retake South Ossetia, a separatist region where most of the population hold Russian passports.

Taking on Ukraine's army would be a very different proposition. Georgia has around 30,000 troops who were quickly trounced. Ukraine has a 200,000 strong military and, as one of the world's top 10 arms exporters, has much more military hardware at its disposal than Georgia.