The U.S. State Department said that a nuclear test by North Korea would constitute a "grave escalatory action" and the United States has various tools to respond.

Vedant Patel, principal deputy spokesperson for the department, said in a press briefing on Wednesday that a seventh nuclear test by the North would seriously threaten regional and international stability and security.

Refusing to elaborate on possible response measures the U.S. could use to hold the North accountable, Patel said simply that Washington has “a number of tools available.”

He also said that the test would undermine the global non-proliferation regime and efforts that are being undertaken to that end. 

The spokesperson added that the recent joint military drills among South Korea, the U.S. and Japan and Washington's fresh sanctions against the North showed the U.S. has options at its disposal.