* Former peace overseer urges West to "act decisively"
* Bosnian Serb leader backs Crimea vote to join Russia
* Bosnia remains deeply divided since 1992-95 war
By Daria Sito-Sucic
SARAJEVO, March 18 (Reuters) - British politician and former Bosnia peace overseer Paddy Ashdown accused Russia on Tuesday of encouraging Serb separatist sentiment in the Western-backed Balkan country in the style of Ukraine's Crimea.
Ethnic Serb leaders in Bosnia, who look to wartime backer Serbia and fellow Orthodox Christian ally Russia for support, have frequently threatened secession since the end of a 1992-95 war in which some 100,000 people were killed.
Ashdown, who served as international peace envoy to Bosnia from 2002 to 2006, urged Europe and the United States to quench separatist tendencies in the country of 3.8 million people, which is still deeply split along ethnic lines.
Russia's seizure of Ukraine's Crimean peninsula, which is majority ethnic Russian, has again stirred dispute over the principle of sovereignty, last tested when the West supported Kosovo's secession from Bosnia neighbour Serbia in 2008 over Russian objections.
"Some Bosnian politicians are playing the Moscow card, even, most dangerously of all, the Slav card, in support of policies of separation," Ashdown told a NATO seminar on southeast Europe in the Bosnian capital Sarajevo.
"They hope that an illegal referendum in Crimea will make one here more likely. And Russia is doing nothing to discourage them - quite the opposite," he said.
Ashdown said it would be a "tragedy" if Bosnia was drawn into "the backwash of international dispute on Ukraine."
"Europe and the West must now act decisively to close down this new salient of division in this country."
SERB LEADER BACKS CRIMEA VOTE
The Bosnian war ended in a U.S.-brokered peace accord that split the country into two highly autonomous regions - a mainly Muslim Bosniak and Croat Federation and a Serb Republic - linked by a weak central authority. Government is highly decentralised and frequently held hostage to ethnic bickering.
Bosnian Serb leader Milorad Dodik has long resisted any efforts to centralise power in Sarajevo, predicting instead the country's eventual demise.
He met Russia's ambassador to Bosnia, Aleksandar Bocan-Harcenko, on Tuesday and said the Serb Republic backed Sunday's referendum in Crimea on joining Russia as "legitimate and democratic", in accordance with international law and the U.N.-guaranteed right to self-determination, Bosnia's Fena news agency reported.
As the Crimea crisis neared its climax last week, Dodik visited Moscow, where he was rewarded by Russian Patriarch Kirill for his efforts "to consolidate the unity of Orthodox nations".
Ashdown noted an offer by Russia of a loan to Bosnia's Serb Republic to compensate for a freeze in funding to both of Bosnia's entities by the International Monetary Fund over stalled economic measures.
Russia stepped in to help Ukraine's pro-Moscow president, Viktor Yanukovich, with billions of dollars in aid after he spurned a deal on closer ties with the European Union in late November. Yanukovich was toppled by mass protests in February, precipitating Crimea's secession by referendum on Sunday.
"The actions of offering an alternative loan ... to one of the (Bosnian) entities, the action of withdrawing support for a project to join Europe, it cannot have any other outcome but to encourage those who wish to see secessionism," Ashdown told reporters.
"Is this just a coincidence? Ask the Russian ambassador." (Editing by Matt Robinson/Mark Heinrich)