China confirmed on Thursday that it had put into a service a new missile that Chinese media has dubbed the "Guam killer" for its ability to hit the U.S. Pacific Ocean base with a conventional or nuclear weapon.

China is in the midst of an ambitious modernization program for its armed forces, developing stealth fighters, aircraft carriers and advanced missiles as it strives to become a world class military by the middle of the century.

That, along with an increasingly assertive stance in the disputed South China Sea and around Taiwan, claimed by China as its sacred territory, has rattled nerves around the region and in Washington.