(Adds foreign trade minister, government spokesman)

By Thomas Grove and Hatice Aydogdu

ISTANBUL, Sept 1 (Reuters) - Turkey began curbing Russian imports on Monday as tensions over Georgia strained NATO'S relations with Moscow.

"Additional trade controls will be applied on Russian goods entering Turkey through third countries," Foreign Trade Minister Kursad Tuzmen told state-run news agency Anatolian.

The measures are in retaliation for delays Turkish exporters have suffered at Russian border crossings since NATO-member Turkey allowed two U.S. ships to transit the Bosphorus Strait to provide aid to Georgia after Moscow's military action there.

"We don't want to apply these measures, but we are acting reciprocally," Tuzmen said.

Russia, which is Turkey's largest trade partner and supplies two-thirds of its natural gas needs, has been angered by what it calls a NATO build-up in the Black Sea, accessed via the Turkish-controlled Strait.

A trade official said the additional measures included checks on Russian goods entering Turkey which were intended to cause delays.

But a government spokesman denied additional controls were being placed on Russian goods entering Turkey. He said he hoped the problem would be solved through diplomacy on Tuesday, when Russian Foreign Minister Sergei Lavrov is due to visit Istanbul.

"Right now things are continuing as normal," said Deputy Prime Minister Cemil Cicek, adding that some attempts had been made to solve the problem. "Tomorrow is an important day. The foreign minister will be in Turkey and there will be a possibility to talk about this issue."

Russia says long inspections of trucks from Turkey are due to a new customs law, but analysts say Moscow may be flexing its economic muscle to put pressure on Ankara.

Turkish business groups said exporters would lose $3 billion in the short term if the delays on goods were kept in place.

Turkey, a close U.S. ally which aspires to join the European Union, has been forced to walk a fine line between its loyalties to NATO and its large financial and energy interests in Russia.

The international community has condemned Russia's campaign in Georgia and its subsequent recognition of Georgian breakaway regions South Ossetia and Abkhazia as independent states.

Turkey has refrained from strong condemnations of Russia. (Writing by Thomas Grove; Editing by Catherine Evans)

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