BRATISLAVA (Reuters) - Slovakia and Ukraine signed a deal on Monday that allows the European Unionto send a limited amount of gas to Ukraine, but providing Kiev with less than it hoped for to cushion the blow should Russia turn off the taps.

Ukraine has been trying to secure alternative supplies to those from Russia's Gazprom since Moscow annexed Crimea last month and Gazprom raised prices for its gas to levels Ukraine is refusing to pay.

Russia's seizure of Crimea from Ukraine has set off the most serious East-West rift since the end of the Cold War, resulting in EU and U.S. sanctions and raising the threat of interruption of gas supplies fromRussia to Europe.

Any supplies Ukraine does contract, however, will likely be from Russia delivered through Slovakia or theNord Stream pipeline running through Germany.

Under the deal, Slovakia will make technical adjustments to an old unused pipeline to ship around 8-9 billion cubic meters (bcm) of gas starting in the autumn. A fallback option would see smaller volumes initially before ramping up to 8 bcm by April.

This means that Ukraine could eventually receive up to around 16-17 bcm per year from EU neighborsPolandHungary and Slovakia, Slovak Prime Minister Robert Fico said. This represents around a third ofUkraine's annual consumption of about 55 bcm.

European Energy Commissioner Guenther Oettinger said the agreement strengthens the ties between the European Union's energy market and that of Ukraine.

"It is a first step for gas flows from Slovakia to Ukraine and strengthens the ties between the EU's energy market and Ukraine," he said in a statement. "Deliveries from EU Member States offer Ukraine access to gas priced on the basis of fair and transparent principles."

Europe takes about a third of its gas imports from Russia, and about 40 percent of that amount flows through Ukraine and into the west via Slovakia.