With India disappointed with Obama, the president has vowed to " work even closer" with its prime minister. Tunku Varadarajan on the cost of ignoring our allies.

On Tuesday evening, the world’s most consequential turbaned man, Manmohan Singh, will glide through White House security and take his place at a dinner table beside Barack and Michelle Obama. He is the prime minister of India, a country that could, if Mr. Obama shoots his diplomatic hoops right, come to be a preeminent American ally in the 21st century, taking its place alongside Britain, Israel, and, assuming the bolshie Yukio Hatoyama doesn’t live forever, Japan.

It doesn’t take a genius to recognize the political, strategic, and moral worth to America, the world’s most powerful democracy, of a strong alliance with India, the world’s largest. Mr. Obama, by no stretch a man of tepid intelligence, has calibrated things artfully: Not only is Mr. Singh the first state visitor to Washington since the president took office in January, his trip is the first time that India has headed an American president’s list for a state visit—ever. (Richard Nixon must be turning in his grave.)

For all his emphasis on diplomacy in dealing with hostile states, Mr. Obama has failed to grasp the diplomatic importance of tending to alliances.

And yet, until this moment, Mr. Obama has been indifferent to India. No doubt his mind has been focused on other matters: the American economy, the wars in Iraq and Afghanistan, Iranian and North Korean nuclear shenanigans—not to mention health-care reform (although one must ask what prompted him to add that burden to an already heaving haversack of misfortune). What has been left of Mr. Obama’s attention has been consumed by China, itself inseparable in so many ways from any resolution of America’s economic crisis. (Treasury Secretary Geithner has done more hard yards on China than Secretary of State Clinton.)

Given all this swirl, Mr. Obama has had scant inclination to pay much attention to, let alone court, Delhi. This has not gone down well in India, a country surrounded by a wall of thin skin. India had grown used, under Mr. Obama’s predecessor, to alpha-dog treatment. George W. Bush was the best American president India ever had, and Mr. Obama’s ability to take India for granted is, in some measure, a tribute to the extent to which Mr. Bush locked the two countries into a presumptively inseparable alliance. But for all his emphasis on diplomacy in dealing with hostile states, like Iran, or inveterate competitor-states, like China, Mr. Obama has failed to grasp the diplomatic importance of tending to alliances, whether they be old and true ones, such as the one with Israel, or young and sensitive ones, such as the one with India.

India is not the India of Eisenhower’s time, or Nixon’s, or Carter’s, or Reagan’s. Sometime in the early 1990s, India finally acquired a “foreign policy” to replace the vexatious, preachy “postcolonial policy” that had previously guided its international relations. Equally, the United States, under Bush, finally acquired an “India policy,” as opposed to a “Pakistan policy” of which India was a mere byproduct. In fact, under Mr. Bush, improved relations between the two democracies came to acquire an almost moral imperative, one than can—and must—survive the short-term reliance on Pakistan in the war against the Taliban in Afghanistan.

In any case, this is a war in which the U.S. has not, so far, been able to count on worthwhile Pakistani support. True, that country has taken pains to maintain the appearance of an ally; but every passing day brings new strains, and new cynicism. Pakistan is “in” so that it can use the war to its advantage in its messianic conflict with India. Besides, its overriding aim is to re-establish a Taliban regime in Kabul: How much plainer does its dissonance with American aims in Afghanistan have to be before Mr. Obama works out that his country’s long-term interests in the region lie with New Delhi, not Islamabad?

Finally, a broader word about India and its relationship with America: Unlike China, which is inherently competitive for global leadership—and which will never accept American leadership or direction—India is a country that would, like Britain or Japan or Germany, settle for a partnership with the United States that guaranteed mutual benefit and respect. India’s natural state, if nations can be said to have such a thing, is neither triumphalist nor antagonist; it is cooperative and redemptive, much as America’s tends to be. One trusts that Mr. Obama will come to see these qualities as clearly as his predecessor did. If not, this could be one area in which history will judge Mr. Obama to have been “dumb,” and Mr. Bush to have been the “smart” one.

Tunku Varadarajan is a national affairs correspondent and writer at large for The Daily Beast. He is also a research fellow at Stanford’s Hoover Institution and a professor at NYU’s Stern Business School. (Follow him on Twitter here.)