U.S. Deputy Secretary of State Wendy Sherman speaks to media after meeting with South Korea's First Vice Foreign Minister Cho Hyun-dong at the Foreign Ministry in Seoul Tuesday. AP-Yonhap

A senior U.S. diplomat warned Tuesday that North Korea would face a "swift and forceful" response should the recalcitrant regime press ahead with a widely anticipated nuclear weapon test.

Deputy U.S. Secretary of State Wendy Sherman issued the warning after she met with her South Korean counterpart, Cho Hyun-dong, in Seoul, to discuss the North's weekend missile launches and the possibility of it conducting what would be its seventh nuclear test.

"Any nuclear tests would be in complete violation of U.N. Security Council resolutions," Sherman told reporters. "There would be a swift and forceful response to such a test."

Sherman added, "The entire world will respond in a strong and clear manner. We are prepared."