As the struggle to control disputed islands and valuable offshore resources has intensified in the East and South China Seas over the past few years, the United States has said repeatedly that it does not take sides in the disagreements among Asian countries over who has ownership rights.
Maintaining an impartial position helps the U.S. to legitimize its "honest broker" role, and thus gain regional acceptance for moves to counter-balance growing Chinese power.
However, this has been easier for the U.S. in the South China Sea than it has in the East China Sea because America's alliance bonds are looser and more ambiguous in the South China Sea, where only one of the four Southeast Asian claimants, the Philippines, is a U.S. ally.