WHEN the United States announced this week that it planned to include India—but not China–on a list of countries exempted from the economic sanctions it intends to impose against countries who buy Iranian oil products, it appeared to be just the latest illustration of Washington diplomats' decidedly divergent views of India and China. For years, America has viewed China as an increasingly powerful and potentially dangerous competitor in trade, geopolitics and virtually everything else. Chinese and American diplomats lock horns routinely. A key focus of America's broader policy agenda has been seeking ways to hedge against the emergence of a stronger and wealthier China. At the same time, it has seen India as a fellow democracy, a “natural ally”, and a potential strategic and military partner in Asia. America has long sold arms to India. In 2005, with the support of George W. Bush, Congress went so far as to make highly irregular exceptions to its own non-proliferation policies under the Non-Proliferation Treaty of 1968 (NPT), clearing the way for a controversial nuclear co-operation deal with India, despite its having never signed the NPT. Barack Obama's administration has played the same upbeat tempo where India is concerned, and it kept it going in Washington this week, where senior officials from both sides meet for their third annual bilateral “Strategic Dialogue”.

Last month in Delhi, in remarks to her Indian counterpart, S.M. Krishna, America's secretary of state, Hillary Clinton, seemed to sum it up: “The United States and India are two great democracies with common values and increasingly convergent interests,”

But not so fast. In a new book, “Chinese and Indian Strategic Behaviour: Growing Power and Alarm”, two American scholars take a methodical and comparative look at Chinese and Indian policy behaviour, defence spending, strategic doctrine, and trade relations. What they found is “that the broad patterns of Indian and Chinese strategic behaviour are not widely divergent.”

The authors are George J. Gilboy, a senior fellow at the Centre for International Studies at the Massachusetts Institute of Technology, and Eric Heginbotham, a senior political scientist at the RAND Corporation, a think-tank. They do not push their findings to argue that America ought to treat the two Asian powers identically. Instead they make a powerful case for an American policy that would be “based on a nuanced, pragmatic realism”. Their view acknowledges vast internal differences between India's democratic system and China's one-party regime. They find however little reason to expect that those differences should offer any useful guidance as to how the two countries' strategic behaviour might affect American interests.

A better guide than regime type, they write, would be the combined influence of a country's history, domestic politics, capabilities, and external balances of power. In their side-by-side comparison, the authors find that both China and India have geo-strategic interests that diverge from America's. They find support for this in the two countries' very similar voting records at the United Nations, and also in the similarity of their approach to issues like those posed today by Syria, Sudan and Iran.

The key to their study, according to Mr Gilboy, was to ask the same questions about both powers.

“That's important because the questions you ask can affect the answers you are likely to get. If you just ask ‘What is the China threat and how can India help?', you are likely to get a certain type of answer, and leave some critical issues with both countries unexamined,” he said.

One critical issue is the expanding need for energy and natural resources in both of Asia's giants. To help meet their demands, both India and China have been willing to do business with what America considers “rogue regimes”. And they do so in similar fashion, using state companies backed by state diplomacy.

Like China, India is heavily invested in the Sudanese oil industry and in the energy sectors of Myanmar, Cuba, and Syria.

But Iran may be the most interesting case. The American decision to deny China a waiver from its new Iranian sanctions regime is not yet final, but Washington's stated intention—to move that way, while promising a waiver to India—is potent on its own.

Apart from its extensive trade interests in Iran, India sees its government as a potential counterweight to Pakistan's influence in Afghanistan. However much sense this calculation makes from an Indian point of view, it would hardly seem to converge with America's best interest.

According to Mssrs Gilboy and Heginbotham, American policy would be better served by a view of India that accounted for such differences. A more even-handed approach towards India would seem to imply, inter alia, an easier line on China.

“Taking rising Indian power seriously means recognising that common democratic values are not simply a substitute for common geo-strategic interests. Comparing the observable track record of actual Indian and Chinese international behaviour shows that the U.S. faces a mixed picture of opportunities and challenges with both,” they say.