Deputy Defense Secretary Robert Work, who witnessed the launch, said the U.S. tests, conducted at least 15 times since January 2011, send a message to strategic rivals like Russia, China and North Korea that Washington has an effective nuclear arsenal.
"That's exactly why we do this," Work told reporters before the launch.
"We and the Russians and the Chinese routinely do test shots to prove that the operational missiles that we have are reliable. And that is a signal ...
And, in case the message was ambiguous,
that we are prepared to use nuclear weapons in defense of our country if necessary."
Demonstrating the reliability of the nuclear force has taken on additional importance recently because the U.S. arsenal is near the end of its useful life and a spate of scandals in the nuclear force two years ago raised readiness questions.