BELGRADE, Serbia -- Serbia on Thursday formally demanded that its security forces return to the breakaway former Serbian province of Kosovo, despite warnings from the West that such calls are unlikely to be accepted and only add to tensions in that part of the Balkans.Serbian President Aleksandar Vucic told state RTS television that the government asked the commander of NATO-led peacekeepers stationed in Kosovo since 1999, when the Western alliance pushed out Serb troops from the region, to allow the return of up to 1,000 Serbian army and police officers to the Serb-populated north of the country.NATO bombed Serbia to stop the war, end its bloody crackdown against ethnic Albanian separatists and civilians and order its troops out of Kosovo.The return of Serbian troops is unlikely to be granted because it would de facto mean handing over security of Kosovo’s ethnic Serb-populated northern regions to Serbian forces — a move that would dramatically increase tensions in the Balkans.Russian Foreign Ministry spokeswoman Maria Zakharova said Thursday that “the Russian Ambassador to Serbia, who is in close contact with the Serbian leadership, has received instructions from the center (Moscow) to take concrete steps of support (to Serbia) which include normalizing or proposing ways to normalize the situation” in Kosovo."