US President Barack Obama (R) addresses Australian troops and US Marines as Australian Prime Minister Julia Gillard listens at RAAF Base Darwin on November 17, 2011. Obama signalled a pivotal US shift to Asia on November 17, pledging not to let Washington’s budget crunch compromise his expansive vision and military presence in the region. AFP PHOTO/Saul LOEB (Photo credit should read SAUL LOEB/AFP/Getty Images)