Poland's Defense Minister has announced that the first of twelve F-16 aircraft from the U.S. and at least 300 service personnel should arrive in Poland on Monday or Tuesday for a training drill. Meanwhile, a U.S. guided-missile destroyer, the USS Truxtun, passed through the Bosphorus Strait on Friday afternoon on its way to the Black Sea.

The training drill involving the F-16 fighter jets will include other airfields besides Lask where a U.S. Air Force detachment is stationed. And the U.S. warship's movements raise fears that the stand-off between Russia and Ukraine and the West over Crimea could become more militarized.

A Turkish coast guard vessel is escorting the U.S. warship during its voyage along the Bosphorus Strait that forms part of the boundary between Europe and Asia.

The U.S. Navy said in a statement that the Truxtun, with 300 sailors on board, left Greece on Thursday en route to the Black Sea and would conduct training with Romanian and Bulgarian naval forces.