China commissioned 17 new warships last year, the most of any nation. In a little more than a decade, China is expected to have three aircraft carriers, giving it more clout than ever in a region of contested seas and festering territorial disputes.

While Beijing still lags far behind the U.S. in both funding and technology, its spending boom is attracting new scrutiny at a time of severe cuts in U.S. defense budgets that have some questioning Washington's commitments to its Asian allies.

Beijing's newfound military clout is one of many issues confronting President Barack Obama on a visit to Asia this week. Washington is faced with the daunting task of fulfilling its treaty obligations to allies such as Japan and the Philippines, while also maintaining cordial relations with China.