The Commerce Department reported that the U.S. trade deficit rose 15.1% in May to the highest level in nearly three years, largely due to the increased cost of oil imports.The trade gap widened to a seasonally adjusted $50.2 billion from $43.6 billion in April, which is the biggest monthly deficit since October 2008.Economists had expected the trade deficit to rise to $44.5 billion.Imports rose 2.6% to $225.1 billion, while exports fell less than 1% to $174.9 billion.