WASHINGTON, DC – MARCH 14: (AFP OUT) U.S. President Barack Obama welcomes British Prime Minister David Cameron during an official arrival ceremony at the South Lawn of the White House March 14, 2012 in Washington, DC. Prime Minister Cameron was on a three-day visit in the U.S. and he was expected to have talks with President Obama on the situations in Afghanistan, Syria and Iran. (Photo by Mark Wilson/Getty Images)