Serbia will open a mass grave on Tuesday believed to contain up to 500 Albanian victims of the Kosovo war, fresh evidence of Serb atrocities as the U.N. decides whether to grant the province independence.

The exhumation will take place at an abandoned quarry in no-man's land between Serbian and Kosovo checkpoints on the 2 km (1.2 mile) wide boundary line.

Authorities believe the bodies were originally buried elsewhere, then dug up, collected, and dumped at the quarry on June 3, 1999, a senior Serbian official told Reuters.

That was a week before NATO called a halt to its 78-day bombing campaign over Serbia and Slobodan Milosevic pulled his forces from the territory, which became a U.N. protectorate.

"We believe that between 300 and 500 bodies can be found there," said the official, who asked not to be named.

"We assume that, as in other cases, the bodies were moved by Serbian forces in order to conceal evidence of atrocities."

The mass grave would be the largest discovered in Serbia since 2001, when the corpses of more than 800 Kosovo Albanians were found in pits on a police training ground outside Belgrade and in eastern Serbia.

Its discovery serves as a gruesome reminder of the rationale behind NATO's first "humanitarian" war in 1999, when 10,000 Albanians died and almost one million took refuge in squalid camps in Albania, Montenegro and Macedonia as Serbia pursued an indiscriminate bid to crush an Albanian insurgency.

More than 2,000 people are missing, the majority Albanians.

The West has circulated a U.N. resolution offering Kosovo a path to statehood, but U.N. veto-holder Russia continues to back Belgrade's insistence that the territory remain within Serbia.

The West wants the U.N. Security Council to vote this month.

Milosevic was ousted in October 2000, extradited to face war crimes charges in 2001 and died in his cell in 2006 months before the court was due to give its verdict on his role in the wars in Bosnia, Croatia and Kosovo.

The chief prosecutor at the U.N. war crimes tribunal, Carla del Ponte, arrived in Belgrade on Monday to assess the commitment of Serbia's new government to hand over the remaining five Serb fugitives.

The European Union froze talks on closer ties with Serbia in May 2006, but says they will restart in June after the extradition last week of Bosnian Serb general Zdravko Tolimir.