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PRESIDENT OBAMA made deft use of diplomatic symbolism when he welcomed Indian Prime Minister Manmohan Singh with the first state dinner of the new administration on Tuesday, calling the relationship between India and the United States “one of the defining partnerships of the 21st century.’’ Coming just after Obama’s high-profile trip to China, Singh’s visit was plainly meant to show that India has nothing to fear from America’s increasing commercial and financial ties to China. While the talks between the two leaders were private, the most useful message Obama could have delivered about the emerging US-India partnership is that America does not want it to be centered on India’s rivalry with China.

Obama confronts challenges elsewhere...