China and Russia are surpassing the United States in acquiring a technology the Pentagon has tried and failed to develop for years: a maneuverable missile that could fly many times the speed of sound and strike anywhere in the world within an hour or two, senior military officials say.

The prospect of losing this arms race has quietly made the development of the hypersonic missile a top priority at the Pentagon, the officials said, as the United States faces rising challenges from superpowers around the world.

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