sofia prime minister bulgaria greece romania give support balkan neighbor serbia bid join european union tuesday say integration western balkans would guarantee regional peace stability serbia 1990s see pariah western balkans central role war follow collapse yugoslavia expect complete negotiations eu membership 2019. us know natural place serbia european union bulgarian prime minister boyko borissov say four-party summit black sea city varna greek prime minister alexis tsipras romanian prime minister mihai tudose serbian president alexander vucic borissov say three eu members would work speed process advantage peace stability balkans europe generally bulgaria take rotate six-month eu presidency january romania take 2019. many serbs however remain skeptical join bloc view western european countries outspoken advocate 1999 nato bomb halt kill expulsion ethnic albanians former province kosovo thousands civilians kill vucic accuse european union use double standards refuse accept catalan independence referendum largely welcome separate kosovo support spain friendly country say vucic european commission respond different way kosovo people state kosovo declaration independence serbia 2008 accept washington eu state reject belgrade ally kosovo gain independence without even hold referendum catalonia ... get anything like vucic say sometimes serbs ask victim double standards serbia position kosovo one main stumble block bid join european union brussels say need improve relations authorities pristina stop try block efforts join international body balkan leaders back serbia 's bid join european union