BELGRADE (Reuter) - The United States called Serbian nationalist presidential candidate Vojislav Seselj a fascist several minutes after the country's election commission said the hardline nationalist was ahead in the counting on Sunday's voting. The outcome of the poll, however, remained uncertain because too low a turnout would render any result null and void. The U.S. envoy for former Yugoslavia, Ambassador Robert Gelbard, said the United States could not work with Vojislav Seselj, adding that he represented "backwardness" and "darkness". Seselj, the Radical Party leader who opposes the Dayton peace process in Bosnia, had at first claimed the turnout would exceed the 50 percent minimum needed. He later conceded he would probably not gain the presidency but expressed confidence that he would secure a re-run of the election later this year. The commission is expected to issue final official results on Thursday evening. In a simultaneous vote in the other republic, Montenegro, two archrivals appeared to be heading for a runoff with neither achieving the 50 percent needed for outright victory.