North Korea firing a Hwasong-18 solid-fuel intercontinental ballistic missile (ICBM) with its leader Kim Jong-un observing the launch is seen in this Dec. 18 file photo provided by the North's official Korean Central News Agency. Yonhap

The United States reaffirmed Tuesday its "ironclad" commitment to South Korea's defense and willingness for dialogue with North Korea, as Pyongyang warned Washington against making a "wrong" choice after its test-firing of an intercontinental ballistic missile (ICBM).

Matthew Miller, the spokesperson for the State Department, made the comments after North Korean leader Kim Jong-un said the latest launch of a Hwasong-18 ICBM shows what option he would take when "Washington makes a wrong decision."

Monday's ICBM launch came with the criticism leveled at the U.S. and South Korea for holding a Nuclear Consultative Group meeting in Washington on the nuclear strategy against the North.

"We have tried to make it a policy of never — not reacting to every provocative statement that he makes," Miller said in a briefing.

"We remain committed to a diplomatic approach to the DPRK and call on the DPRK to engage in dialogue. We harbor no hostile intent to the DPRK," he said, referring to North Korea by its official name, the Democratic People's Republic of Korea.

"And our commitments to the defense of the Republic of Korea and Japan remain ironclad," Miller added.

John Kirby, National Security Council coordinator for strategic communications, stressed U.S. efforts to revitalize alliances and partnerships against growing North Korean threats.

"We've added military capabilities to the region, including intelligence-collection capabilities. And that's not going to change," he said.

"We take our responsibility seriously to our allies, Japan and the Republic of Korea," he said. The Republic of Korea is South Korea's official name. (Yonhap)