MOSCOW, Sept 13 (Reuters) - Russia's food safety watchdog threatened on Tuesday to ban imports of some citrus fruits from Egypt, escalating a trade dispute over Cairo's delay in approving Russian wheat shipments.

Moscow is seeking talks with Egypt, the world's biggest wheat importer and the top buyer of Russian wheat, because Cairo has not approved any Russian wheat imports since it tightened regulations on the ergot wheat fungus late August.

Ahead of large citrus fruit shipments to Russia from Egypt, the Rosselkhoznadzor watchdog said in a statement it was concerned about the "systematic breach of international and phytosanitary requirements" by the Egyptian supplies.

It did not disclose the list of the products that could be banned and did not answer a call from Reuters. Egypt's Agriculture Ministry did not provide an immediate comment.

Russia imported 1.5 million tonnes of citrus fruits from across the world in 2015 worth $1.2 billion, according to the customs data.

It was not immediately clear whether there were any political motives behind the statement. Russia has a history of using threats and import limits from the food safety watchdog in trade disputes with other countries.

The threat could strengthen Moscow's position in talks with Cairo over the delayed wheat supplies. Russia is keen to restore exports to Egypt as soon as possible following the largest wheat crop in its post-Soviet history. (Reporting by Polina Devitt; Additional reporting by Eric Knecht; Editing by Maria Kiselyova and Mark Potter)