The world's three most populous countries are locked in a power struggle across the Indo-Pacific region. The United States wants to strengthen its defense partnership with India as part of a broader effort to counter China's growing influence in the region and around the world. India, too, is interested in challenging China by asserting itself in Southeast Asia's political, economic and security domains as it pursues its "Act East" policy. But although they share a rival in common, Washington and New Delhi have different aims in their efforts against Beijing. The divergences in their strategies will get in the way of greater cooperation in the region between the United States and India....