Since the end of the Cold War in 1991 there has been a major shift in naval power in the Indian Ocean. With the demise of the Russian fleet (seen as an Indian ally) and the rise of Chinese naval power, India has sought cooperation from a growing U.S. Navy presence in the area. This is all about keeping Indian naval power supreme in the Indian Ocean. The rising Chinese threat is seen as more than India can handle alone. With Indian inability to expand, or even maintain their current naval power more help has to come from somewhere.
While India was technically neutral during the Cold War, India was generally hostile to the United States and quite cozy with Russia. India still has good relationships with Russia, but the Russians have no fleet to speak of these days and suddenly the Americans are seen as potential allies. In part this is because the anti-American slant was more the product of Indian post-colonial nationalism (that was generally anti-Western) and infatuation with socialism. Both those policies proved failures and, while many Indian politicians do not accept the shift to a market economy and better relations with the West, these changes have happened anyway.
But above all this there is China, which has already taken some disputed territory on the Indian border and claims still more. Chinese ships (both commercial and military) are more frequently seen in the Indian Ocean. Chinese shipping firms have refurbished ports throughout the region and manage them to handle growing Chinese trade with the countries where these ports are located. The Chinese presence cannot be ignored and the Indians are now welcoming the Americans.
Yet there won’t be a lot of Americans. The U.S. defense budget is declining and so is the size of the American fleet. Most of the U.S. naval presence in the Indian Ocean is in and around the Persian Gulf and is there mainly to curb growing Iranian aggression. The only major American base actually in the Indian Ocean is Diego Garcia (a 44 square kilometer island 4,700 kilometers south of Afghanistan).
The U.S. Navy maintains a base in Bahrain in the Persian Gulf and several Gulf states host American warplanes. What India wants is some American warships closer to the Indian coast. That does not seem to be happening soon enough to influence the Chinese fleet moving into the region.