BELGRADE (Reuters) - Serbia, which treads a delicate line between U.S.-led NATO and traditional ally Russia, is to hold joint air force exercises with Russia this year, the defense ministry said on Monday.

Russia’s ally, Belarus, will join units from the Serbian and Russian air forces in the first exercise called “Slav Brotherhood 2016” to be held in autumn, the ministry said in a written statement.

“It represents the continuation of the cooperation between the two air forces that began in 2014 with a joint military exercise,” it said.

Another similar exercise would be held just between Serbia and Russia later.

The Balkan state is performing a delicate balancing act between its European aspirations, partnership with NATO and its centuries-old religious, ethnic and political alliance with Russia.

Though Serbia aspires to join the European Union and has taken part in partnership programs with NATO, it is not actively pursuing membership of the U.S.-led alliance which remains unpopular among Serbs because of its 1999 bombing campaign to drive Serbian forces out of Kosovo.

Serbia shares Slavic and Orthodox Christian traditions with Russia and depends on it for energy. The warm relationship has been nurtured by Russia which prevented Kosovo from becoming a member of the United Nations, at Belgrade’s request.