By Angelika Stricker and Sebastian Moffett

BRUSSELS (Reuters) - NATO plans to refocus its security operation in Kosovo on a mostly Serb northern border region after major contributor Germany said the EU's police force was "on the wrong track" and placing too great a burden on NATO forces there, officials said on Wednesday.

Western powers formally ended their role overseeing Kosovo in September, four years after it proclaimed independence. But the European Union's police force, EULEX, and a 6,000-strong NATO force remain to deal with occasional ethnic violence.

A tiny part of the northernmost border region is particularly problematic, as about 50,000-60,000 Serbs there reject the independence of the former Serbian province and oppose the Pristina government, challenging NATO and EU troops.

Following the complaint from Germany - with 1,330 security personnel, the biggest contributing NATO ally in Kosovo - NATO's head said there would be a change in focus.

"I think you will see you will see some rebalancing in the coming months, with a stronger focus on the north of Kosovo," NATO Secretary General Anders Fogh Rasmussen told reporters after a two-day meeting of alliance defense ministers. This, he said would be done "taking into account the volatile situation we have witnessed there".

German Defense Minister Thomas de Maiziere said he expected a proposal on the revamp in coming weeks from NATO's Supreme Allied Commander Europe, followed by a decision at the next meeting of NATO defense ministers in February.

Berlin is particularly concerned about Kosovo, as along with the United States, Italy and Austria, it foots much of the bill for low-level peacekeeping work. Speaking ahead of Wednesday's meeting, De Maiziere said he would push for EULEX to be completely overhauled.

"Germany is not satisfied with the situation," he told reporters on Tuesday evening. "We need a new start, a new name, a new structure, new people and a new mandate. In any case, it's on the wrong track. We need to sort that out at the EU level."

EU foreign affairs spokeswoman Maja Kocijancic said that all EU countries, including Germany, had signed off on a revamped, two-year mandate for EULEX just four months ago.

UNEQUAL BURDEN

Unlike NATO, EULEX was not accepted by Serbs as a neutral force, De Maiziere said, meaning that NATO reservists - in particular German, Italian and Austrian - were being forced to do work that should be done by the Kosovo police and EULEX.

"I underlined that we expect a new direction in troop distribution, so that we don‘t always have to rely on reservists," De Maiziere told reporters after Wednesday's meeting. "That will now happen."

De Maziere's intervention in the debate comes after the 28-member military alliance had been considering cutting troop numbers. But plans to trim the NATO peacekeeping force were put on hold last year after a spate of violence in the north.

On Tuesday, the minister said that if fewer soldiers were needed, NATO should take such a decision. "But to act as if we need fewer and then to get the job done through reservists - that is not right," he said.

More than 50 people were injured in clashes in June when the authorities in Kosovo deported a group of visiting Serbs who accused the police of shooting at them, leaving one with life-threatening gunshot wounds.

Serbia lost control of Kosovo in 1999 when NATO bombed it to halt the killing and expulsion of ethnic Albanians by Serb forces fighting a two-year counter-insurgency war.

Landlocked and impoverished, Kosovo has been recognized by 91 countries including the United States and 22 of the EU's 27 members.

Serbia is under pressure from the EU - which it wants to join - to loosen its grip on north Kosovo and to improve relations with Pristina.

(Additional reporting by Fatos Bytyci; Editing by Louise Ireland)