By Douglas Hamilton

BELGRADE, Sept 16 (Reuters) - Prime Minister Vojislav Kostunica's party told President Boris Tadic on Sunday to keep out of foreign policy, as a split in their coalition deepened over whether Serbia's future lies with the West or with Moscow.

"The president has no authority to make or carry out foreign policy (and he) is well aware of his constitutional position and capacities," party spokesman Branislav Ristivojevic said.

Kostunica and his party are leaning increasingly towards Russia as a true friend of their country and away from the European Union and NATO, which want Serbia to concede the independence of breakaway Kosovo province and hand over war crimes fugitives.

Russia has boosted Kostunica's confidence by blocking a Western-backed proposal in the United Nations that would have made the 90 percent ethnic Albanian province independent.

Ristivojevic's statement, the latest in a public clash of ideas over the country's future, followed a decision by Kostunica's party on Saturday to oppose joining NATO, which prompted a statement by Tadic that Euro-Atlantic integration was Serbia's priority.

Tadic is "as obliged as any other state official to respect official state policy, and the Serbian government has never decided that this state should join NATO," Ristivojevic told local television.

RHETORICAL EXCESS?

Tadic and Kostunica are political rivals who buried significant differences this year to create a united front against Kosovo's independence.

But Kostunica's party has taken anti-Western rhetoric beyond the limits of what Tadic's party can accept, constantly attacking the United States, NATO and the EU while lauding Russia and suggesting Serbia's destiny does not lie with the West.

Serbian Foreign Minister Vuk Jeremic, a member of President Tadic's Democratic Party, has had to "clarify" the latest bellicose statements from Kostunica's circle each time he travels to the West.

Tadic, whose party outpolls Kostunica by well over two to one, wants a presidential election this year. Kostunica is opposed, insisting the country must close ranks ahead of a showdown on Kosovo expected in December.

Some analysts suggest the coalition may collapse, but Kostunica, declaring an emergency, might hold onto power with the support of the ultranationalist Radical Party which is even more anti-Western.

The junior coalition partner in the government, G17 Plus, said on Sunday it supported EU and NATO membership.

"Considering that Serbia has a multi-party system and a coalition government, it is necessary that parties reach agreement on this issue. But the final ruling will come from citizens in a referendum when the time comes," said party spokesman Nikola Papak.

Serbia has joined NATO's Partnership for Peace programme, which also has Switzerland and Uzbekistan as members, among many other states not full members of the Western alliance.

Serbia has not yet been invited to join NATO so raising the issue is simply harmful political posturing, Papak told Beta news agency. (Additional reporting by Gordana Filipovic)

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