MOSCOW, April 11 (Reuters) - Russia may suspend charter flights to Turkey due to the "difficult political situation" there, the Federal Air Transport Agency has warned airlines, a source at one of the companies told Reuters.

Russia and Turkey have a history of rolling trade and financial restrictions out against one other in political rows. Ties between Moscow and Ankara have become strained in recent days after Turkey called for Syrian President Bashar al-Assad, a staunch Russian ally, to step down.

The Federal Air Transport Agency declined to comment.

If Russia goes ahead with the suspension, it could seriously hurt Turkey's already battered tourism industry which relies heavily on visitors from Russia.

The Kommersant newspaper reported that, according to preliminary data, Russian travel agents have already sold up to 400,000 package tours to Turkey. In total, it said 3 million Russian tourists were expected to visit this year.

For Russia, Turkey is an important agricultural buyer and news that Russia is mulling a charter ban comes weeks before Moscow and Ankara are expected to discuss why Ankara put purchases of Russian wheat, maize and sunflower oil on hold by imposing high import tariffs from mid-March.

(Reporting by Gleb Stolyarov; Writing by Polina Devitt; Editing by Andrew Osborn) ((; +7 495 775 12 42; Reuters Messaging: