Crowds await the arrival of British Prime Minister David Cameron at the official arrival ceremony on 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.
- [Mark Wilson/AFP/Getty Images]

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.
- [Mark Wilson/AFP/Getty Images]

British Prime Minister David Cameron inspects the troops during an official arrival ceremony at the South Lawn of the White House March 14, 2012 in Washington, DC. Prime Minister Cameron is 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.
- [Mark Wilson/AFP/Getty Images]

U.S. President Barack Obama (L) and British Prime Minister David Cameron greet guests and school children during an official arrival ceremony on the South Lawn of the White House March 14, 2012 in Washington, DC. Cameron was on a three-day visit in the U.S. and he was expected to have talks with Obama on the situations in Afghanistan, Syria and Iran.
- [Chip Somodevilla/AFP/Getty Images]

British Prime Minister David Cameron (L) speaks while U.S. President Barack Obama listens during an official arrival ceremony at the South Lawn of the White House March 14, 2012 in Washington, DC. Prime Minister Cameron is on a three-day visit in the U.S. and he is expected to have talks with President Obama on the situations in Afghanistan, Syria and Iran.
- [Mark Wilson/AFP/Getty Images]

U.S. President Barack Obama (R) talks to British Prime Minister David Cameron (L) during a meeting in the Oval Office of the White House March 14, 2012 in Washington, DC. Cameron is on a three-day visit to the U.S. and he is expected to have talks with Obama on the situations in Afghanistan, Syria and Iran.
- [Alex Wong/AFP/Getty Images]

U.S. President Barack Obama, British Prime Minister David Cameron, U.S. first lady Michelle Obama and Samantha Cameron wave from a balcony during in an official arrival ceremony on the South Lawn of the White House March 14, 2012 in Washington, DC. Cameron is on a three-day visit to the U.S. and he is expected to have talks with Obama on the situations in Afghanistan, Syria and Iran.
- [Alex Wong/AFP/Getty Images]

First Lady Michelle Obama (R) and Samantha Cameron talk during the official arrival ceremony at the South Lawn of the White House March 14, 2012 in Washington, DC. Prime Minister Cameron is on a three-day visit to the U.S. and he is expected to have talks with Obama on the situations in Afghanistan, Syria and Iran.
- [Chip Somodevilla/AFP/Getty Images]

U.S. President Barack Obama (R) and British Prime Minister David Cameron review the U.S. Army's Old Guard Fife and Drum Corps during an official arrival ceremony on the South Lawn of the White House March 14, 2012 in Washington, DC. Cameron is on a three-day visit to the U.S. and he is expected to have talks with Obama on the situations in Afghanistan, Syria and Iran.
- [Alex Wong/AFP/Getty Images]

U.S. President Barack Obama (R) and first lady Michelle Obama wait for the arrival of British Prime Minister David Cameron during an official arrival ceremony on the South Lawn of the White House March 14, 2012 in Washington, DC. Prime Minister Cameron is on a three-day visit to the U.S. and he is expected to have talks with Obama on the situations in Afghanistan, Syria and Iran.
- [Chip Somodevilla/AFP/Getty Images]

U.S. President Barack Obama (R) and British Prime Minister David Cameron participate in an official arrival ceremony on the South Lawn of the White House March 14, 2012 in Washington, DC. Prime Minister Cameron is on a three-day visit to the U.S. and he is expected to have talks with Obama on the situations in Afghanistan, Syria and Iran.
- [Chip Somodevilla/AFP/Getty Images]

First Lady Michelle Obama (R) and Samantha Cameron talk during the official arrival ceremony at the South Lawn of the White House March 14, 2012 in Washington, DC. Prime Minister Cameron is on a three-day visit to the U.S. and he is expected to have talks with Obama on the situations in Afghanistan, Syria and Iran.
- [Chip Somodevilla/AFP/Getty Images]

U.S. President Barack Obama (R) shakes hands with British Prime Minister David Cameron during a joint press conference in Rose Garden of the White House on March 14, 2012 in Washington, DC. Prime Minister Cameron is on a three-day visit to the U.S. and he is expected to have talks with Obama on the situations in Afghanistan, Syria and Iran.
- [Mark Wilson/AFP/Getty Images]

U.S. President Barack Obama (R) speaks while British Prime Minister David Cameron listens during a joint press conference in Rose Garden of the White House on March 14, 2012 in Washington, DC. Prime Minister Cameron is on a three-day visit to the U.S. and he is expected to have talks with Obama on the situations in Afghanistan, Syria and Iran.
- [Chip Somodevilla/AFP/Getty Images]

U.S. President Barack Obama (R) and British Prime Minister David Cameron walk away after holding a joint news conference in the Rose Garden of the White House March 14, 2012 in Washington, DC. Cameron was on a three-day visit in the U.S. and he was expected to have talks with Obama on the situations in Afghanistan, Syria and Iran.
- [Mark Wilson/AFP/Getty Images]