Chinese President Hu Jintao, left, and Vice President Joe Biden stand for the national anthems of both countries during an arrival ceremony on Tuesday, Jan. 18, 2011, at Andrews Air Force Base, Md. (AP Photo/Evan Vucci)
Chinese President Hu Jintao and Vice President Joseph R. Biden Jr. walk the red carpet upon Mr. Hu's arrival Tuesday at Andrews Air Force Base, Md., for the start of a state visit. China's trade with Iran will be one of many thorny issues President Obama will likely raise with Mr. Hu. (Associated Press)
President Obama returns a salute as he and daughter Sasha arrive with his wife, Michelle, and other daughter Malia at Andrews Air Force Base in Maryland on Tuesday after nearly two weeks of vacation in Hawaii. (Associated Press)
President Obama salutes as he leaves Marine One before boarding Air Force One at Andrews Air Force Base on Tuesday, Aug., 31, 2010, for a trip to Fort Bliss, the sprawling Army base in El Paso, Texas, where he will speaks to the troops. (AP Photo/Pablo Martinez Monsivais)
President Obama walks up the steps of Air Force One at Andrews Air Force Base Md., Monday, Aug. 16, 2010. Mr. Obama is embarking on a three-day tour to raise money for Democrats, beginning in Wisconsin where he will visit ZBB Energy Corp, to underscore what he said was his lasting commitment to a clean energy future.
President Barack Obama and Transportaion Secretary Ray LaHood walk on the South Lawn of the White House in Washington, Friday, July 30, 2010, prior to boarding his helicopter for a short flight to Andrews Air Force Base, then on to Michigan where he will tour General Motors and Chrysler factories recovering from the financial crisis. (AP Photo/J. Scott Applewhite)
Sen. Carl Levin, D-Mich, talks on a cell phone as walks towards Air Force One at Andrews Air Force Base, Md., Friday, July 30, 2010, prior to boarding ahead of President Barack Obama, for a flight to Michigan. (AP Photo/Cliff Owen)