The United States is warning North Korea against irresponsible provocations after North Korea said it had restarted normal operations at its Yongbyon nuclear center.

U.S. presidential spokesman Josh Earnest said Tuesday that North Korea should stop itself from actions that serve only to aggravate” tensions in East Asia. He urged North Korea to work instead on honoring the international agreements it has signed.

Earlier, North Korea warned it is ready to use nuclear weapons against the United States at "any time." The Korean Central News Agency published the warning. North Korea also threatened to use ballistic missile technology to launch a weather satellite into orbit. The United Nations Security Council has barred North Korea from using such technology.