WASHINGTON (Reuters) - U.S. President Donald Trump intends to nominate a Raytheon Co (RTN.N) lobbyist, Mark Esper, for the position of secretary of the Army, the White House said on Wednesday. The position has been challenging for Trump to fill. Two previous nominees withdrew their names from consideration. Before Esper joined U.S. missile maker Raytheon in 2010 as vice president government relations he held posts at industry advocacy groups like the Aerospace Industries Association and the U.S. Chamber of Commerce. Esper graduated from the United States Military Academy at West Point, retired from the U.S. Army as a lieutenant colonel and is a veteran of the Gulf War, according to a Raytheon memo announcing his hiring. 