"This launch is in violation of multiple UN Security Council Resolutions and poses a threat to the DPRK's neighbors and the international community," a State Department spokesperson said, referring to the North by its official name, the Democratic People's Republic of Korea.

"We remain committed to a diplomatic approach to the DPRK and call on them to engage in dialogue," he said.

The spokesperson also said that the US commitment to defend both South Korea and Japan, two treaty-bound allies, was "ironclad."

US Secretary of State Antony Blinken and Defense Secretary Lloyd Austin are already set to meet virtually Thursday for regular security talks with their Japanese counterparts.

They will be joined by the new US ambassador to Tokyo, Rahm Emanuel, the former Chicago mayor who was confirmed by the Senate despite opposition.

President Joe Biden's administration has repeatedly said it is open to talks with North Korea, which has pursued a series of mostly low-level projectile launches.

North Korea's leader Kim Jong Un held three high-profile meetings with Biden's predecessor Donald Trump but the unusual personal diplomacy did not bring any lasting agreement.

The South Korean military said the North fired what is "presumed to be a ballistic missile" towards the sea east of the peninsula from Jagang province, which borders China.