The decision was made at a meeting of the ruling party's military commission presided over by leader Kim Jong Un, according to the official Korean Central News Agency (KCNA).

"The meeting discussed and adopted the important practical steps for making more effective, powerful and offensive use of the war deterrent," KCNA said.

The report said the move was aimed at "coping with the present situation in which the war provocations of the U.S. and south Korea are reaching the red-line," but did not elaborate on the measures.

South Korea and the United States are scheduled to start the "Freedom Shield" exercises Monday, focusing on the "changing security environment" due to North Korea's redoubled aggression, the allies said.

All such exercises infuriate North Korea, which views them as rehearsals for an invasion.

The country has said its nuclear weapons and missile programmes are for self-defence.

Analysts have said North Korea will likely use the drills as an excuse to carry out more provocations, including missile tests and perhaps even a nuclear test.

On Friday KCNA reported that Kim ordered North Korea's military to intensify drills for a "real war".

While inspecting a fire assault drill, Kim told soldiers to be prepared for "two strategic missions, that is, first to deter war and second to take the initiative in war", according to KCNA.

Washington and Seoul have ramped up defence cooperation in the face of growing military and nuclear threats from North Korea, which has conducted ever more provocative banned weapons tests in recent months.