U.S. Defense Secretary Chuck Hagel has wrapped up a tour of the U.S. Navy cruiser Vella Gulf, the deadliest U.S. vessel deployed to the Black Sea since the Russian annexation of Ukraine's Crimean Peninsula, AP reported. Hagel had lunch with sailors and reviewed the ship's high-tech ballistic missile defense systems Thursday. The guided missile cruiser is on a port call off the Romanian city of Constanta. It is the fourth U.S. ship to sail into the Black Sea recently as part of a series of U.S. military moves designed to reassure European allies of an American commitment to their security amid tensions over Ukraine. The ship has been in the Black Sea for nearly two weeks and arrived in Romania Tuesday.