US President Barack Obama (2ndR), US Vice President Joseph R. Biden (R), Britain's Prince Charles (2ndL) and his wife Camilla, Duchess of Cornwall, wait for a meeting in the Oval Office of the White House March 19, 2015 in Washington, DC. AFP PHOTO/BRENDAN SMIALOWSKI (Photo credit should read BRENDAN SMIALOWSKI/AFP/Getty Images)

US President Barack Obama (2ndR), US Vice President Joseph R. Biden (R), Britain's Prince Charles (2ndL) and his wife Camilla, Duchess of Cornwall, wait for a meeting in the Oval Office of the White House March 19, 2015 in Washington, DC. AFP PHOTO/BRENDAN SMIALOWSKI        (Photo credit should read BRENDAN SMIALOWSKI/AFP/Getty Images)