President Barack Obama arrives this week in an Australia whose economy is reliant on billions of dollars in mineral and energy contracts from emerging superpower China and whose security depends on an alliance with the U.S. — China's biggest rival.

Personal ties between Obama and Prime Minister Julia Gillard, born within two months of each other, underscore the nations' political bonds as China expands its security interests toward southeast Asia. Obama, the first black U.S. president, and Gillard, Australia's first woman prime minister, share a struggle to overcome resistance to their agendas — from universal health care in the U.S. to a mining tax in Australia.

“This relationship between Obama and Gillard has some warm, fuzzy atmospherics — their interests are congruent,” said Michael McKinley, a lecturer in international relations at the Australian National University in Canberra. “China is the elephant in the room for Obama and Gillard,” said McKinley, whose analysis has been used in parliamentary testimony.