The Pentagon ordered the deployment of the anti-ballistic missile weapon, known as the Terminal High Altitude Area Defense system (THAAD), on Wednesday, according to a department statement.
On Tuesday, Pentagon announced was deploying the USS Decatur and USS McCain into the Western Pacific, as part of a "missile defense mission" in the region, according to DOD Press Secretary George.
Both Arleigh Burke-class Navy destroyers are equipped with the Aegis missile defense system, which is essentially a sea-based version of the THAAD anti-missile weapon.
That same day, Rep. Peter King (R-N.Y.) suggested the United States had the right to take preemptive military action against North Korea if there was "solid evidence" that Kim Jong Un planned to attack the U.S. or South Korea.
"I don't think we have to wait until Americans are killed or wounded or injured in any way," King told CNN.
"I'm not saying we should be rushing into war ... but if we have solid evidence that North Korea's going to take action, then I think we have a moral obligation and an absolute right to defend ourselves," he added.
However, both deployments are strictly defensive measures designed to "strengthen defense capabilities for American citizens in the U.S. Territory of Guam" as well as other American positions in the Asia-Pacific, according to the department.
The move is the latest step in ongoing escalation of military force between Washington and Pyongyang.
Last week, North Korean dictator Kim Jong Un reportedly ordered his forces to begin plans to launch strikes against Guam, Hawaii and the U.S. mainland.
North Korea has also its long-range artillery and rocket units aimed at Seoul on full alert and shuttering a military hotline with South Korea. Earlier this month, Pyongyang officially terminated the 1953 armistice with South Korea that ended the Korean War.
In response, U.S. forces began flying B-2 and B-52 heavy bombers, which are capable of carrying nuclear weapons, in the skies above South Korea.
On Wednesday, Defense Secretary Chuck Hagel spoke by phone with China's new defense chief Chang Wanquan about the growing North Korean threat to the U.S. and its allies.
During the call, Hagel emphasized "the importance of sustained U.S.-China dialogue and cooperation on these issues" given Beijing's role as North Korea's main economic and political ally.
The escalating crisis with North Korea was prompted by Pyongyang's recent, repeated violations of United Nations sanctions on the country's ongoing nuclear and long-range missile tests.
Kim has also threatened to launch nuclear attacks against both South Korea and the U.S. once North Korea is able to obtain that long-range strike capability.