Istanbul - A U.S. warship passed through Turkey's Bosphorus straits on Friday on its way to the Black Sea, in what the U.S. military has described as a "routine" deployment scheduled well before the crisis in Ukraine.

Washington announced the deployment on Thursday, a day after the Pentagon unveiled plans to put more U.S. fighter jets on a NATO air patrol mission in the Baltics in a bid to reassure allies alarmed by Russia's effective seizure of Ukraine's Crimea peninsula, which juts into the north of the Black Sea.

Crimea is home to Russia's Black Sea military base in Sevastopol.

Turkish television showed the USS Truxton, a navy guided-missile destroyer, heading north through Istanbul towards the Black Sea, where it was due to conduct training exercises with naval forces from NATO allies Bulgaria and Romania.