Tokyo and Washington are struggling to keep a feud over a U.S. military base from spoiling President Barack Obama's visit next month, but assuaging mutual anxiety as both allies adapt to China's growing clout will be an even harder task. "There is more raison d'etre to the alliance than ever before, but they have to reframe it and take it out of the Cold War context," said Daniel C. Sneider at Stanford University's Shorenstein Asia-Pacific Research Center.