Turkey has scrambled jets after Russian surveillance plane flew along Turkey's Black Sea Coast, shortly after a US destroyer deployed in the area.
The report comes amid heightened tension over the crisis in Ukraine.
The USS Truxtun passed the Dardanelles strait earlier today on its way to the Black Sea, amid reports that Russia has now 30,000 troops in Crimea.
The US Navy said in a statement that the Truxtun would conduct training with Romanian and Bulgarian naval forces.An F-15 jet fighter
"While in the Black Sea, the ship will conduct a port visit and routine, previously planned exercises with allies and partners in the region," it said.
Crimea is home to Russia's Black Sea military base in Sevastopol.
The Obama administration has taken steps to support the defences of US allies in Europe.
The Pentagon sent six US F-15 fighter jets in Lithuania to bolster air patrols over the Baltics.
The fighter jets and 60 US military personnel landed at Siauliai Air Base in Lithuania, adding to the four F-15s and 150 troops already there to do the air patrol mission.
The warship, which has a crew of about 300 sailors, is part of an aircraft carrier strike group that deployed from the US in mid-February.
"This type of ship is one of the mainstays of the US navy, pretty advanced, relatively recent," said defence analyst Francis Tusa.Troops believed to be Russian in Crimea
Mr Tusa said that while military training exercises are routine, on this occasion the US appeared to make sure "people were aware that this was happening" to raise its profile.
"It's almost perfect," he told Sky News.
"You can both make the Russians aware the ship is going into the Black Sea - but it's a pre-planned deployment, so you're not flooding the area with a fleet.
"It's best of both worlds."
President Barack Obama is stepping up the pressure.
He ordered sanctions on people responsible for Moscow's military intervention in the Crimean peninsula, including travel bans and freezing of their US assets.
He also said a referendum by the region to join Russia would violate international law.
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