The statement comes a few days after the North Korean leader announced his country is ready to test an intercontinental ballistic missile.
Department spokesman John Kirby made the statement the same day the White House said nothing has changed in its assessment of North Korea's nuclear and missile programs, Yonhap reported.
North Korea sent shockwaves around the world after Kim said in a televised statement on Sunday the country is almost ready to test an intercontinental ballistic missile.
Kim also vowed to continue the development of the weapons as long as the United States remains committed to holding military exercises on the Korean peninsula.
On Tuesday Kirby said the U.S. military stands ready deter Pyongyang's biggest threats, owing to a policy of rebalancing in the Asia-Pacific.
"There is a military component to the Asia Pacific rebalance that the United States has pursued, and we have the majority of the U.S. Navy in the Pacific region," Kirby said. "We've moved special radars into place."
At the White House, spokesman Josh Earnest said there was "no change" in the assessment of North Korea's nuclear and missile development, and any changes in the assessment would come from the intelligence community.
Seoul is taking North Korea's weapons program seriously and is to launch in 2017 a special unit assigned to strike the North Korean leadership, two years ahead of schedule, according to Yonhap.
"We are planning to set up a special brigade with the goal of removing or [at least] paralyzing North Korea's wartime command structure [in the face of escalating threats]," Han said.