The United States will strengthen its presence in the Black Sea region using part of a $1 billion fund promised to NATO allies on Russia's borders, and will continue to send warships to the area, Defence Secretary Chuck Hagel said in Romania on Thursday, according to AP. Hagel is the latest high-ranking American official to visit Europe since Russia's annexation of Crimea, as Washington looks to reassure allies jittery about Moscow's intentions in its former Cold War backyard. Hagel was on a visit to the Romanian port Constanta, which recently hosted U.S. ships carrying out the navy exercises and where the Aegis guided missile cruiser USS Vella Gulf is currently berthed. The $1 billion fund will allow for a "stronger presence of U.S. ships in the Black Sea", Hagel said, adding that the presence of the Vella Gulf was an expression of Washington's commitment to regional security. "We will sustain that tempo going forward," Hagel told reporters, referring to the rotating presence of U.S. ships in the Black Sea since the Crimea crisis erupted.