"The United States calls on the DPRK to refrain from further provocations and enter into a substantive dialogue," RIA Novosti quoted her as saying.
Thomas-Greenfield noted the need to continue the sanctions pressure against North Korea.
“Our position is clear - the DPRK must comply with the UN Security Council resolutions and the time has come to start a substantive dialogue with a view to the complete denuclearization of the Korean Peninsula,” the diplomat added.
Earlier, the Committee of the Chiefs of Staff of the South Korean Armed Forces said that the DPRK had launched a ballistic missile towards the Sea of Japan.
Japanese Prime Minister Fumio Kishida also confirmed that two missiles were fired from North Korea towards the Sea of Japan, which are most likely ballistic missiles.
The US military condemned the missile launches.
The UN expressed concern over the new missile launches of the DPRK.