Called the W-88, it is small enough so that each missile can carry up to 10 warheads - each one powerful enough to destroy an entire city. Now China has tested a warhead very much like the W-88.
Beginning in 1992, the Chinese conducted a series of underground nuclear tests of a weapon which used the same trigger concept as the W-88 - an important first step toward deploying intercontinental ballistic missiles with multiple warheads.
"Now they're gonna be able to put multiple warheads on top of smaller solid fuel missiles. It means they can have more nuclear weapons aimed at the United States," said Jonathan Pike of the Federation of American Scientists.
Pike said multiple warheads, like the ones carried by American missiles also would make China a much more dangerous country to attack.
"The benefit of having multiple warheads on a single missile is that if only a few of their missiles manage to survive an attack they would still have enough nuclear firepower to devastate a potential adversary," Pike said.
China has no lack of short-range missiles, but only 13 missiles capable of hitting targets in the U.S. Officials say they do not expect the Chinese to actually deploy multiple warheads for at least 10 years. So it's not yet a threat, but China now has the ability to deploy a modern nuclear force.