The United States urged North Korea on Monday to refrain from menacing actions and rhetoric after North Korean leader Kim Jong-un threatened to conduct yet another nuclear test and more ballistic missile launches.

Pyongyang's Korean Central News Agency reported that leader Kim declared "a nuclear warhead explosion test and a test-fire of several kinds of ballistic rockets able to carry nuclear warheads will be conducted in a short time to further enhance the reliance of nuclear attack capability."

It was the latest in a series of nuclear and missile threats the communist nation has made in recent weeks as South Korea and the United States have been conducting annual joint military exercises that Pyongyang has branded preparation for a northward invasion.

"We urge North Korea to refrain from provocative actions and rhetoric that aggravate tensions and instead focus on fulfilling its international obligations and commitments," State Department spokesperson Anna Richey-Allen said in comments to Yonhap News Agency.

The North conducted its fourth nuclear test on Jan. 6 and a long-range rocket launch a month later in defiance of international warnings. In response, the U.N. Security Council adopted the harshest-ever sanctions on Pyongyang earlier this month.

Pyongyang's recent threats are believed to be a message to the outside world that it remains unfazed by the new sanctions and will forge ahead with nuclear and missile development. They are also believed to be designed to assert Kim's leadership in the lead-up to a key Workers' Party Congress in May. (Yonhap)