The Pentagon said Friday that America's annual military exercise with South Korea has resumed after being stopped as a result of escalating tensions and threats of war from Pyongyang.

David Shear, the assistant secretary for Asia issues, told Pentagon reporters that the exercise was temporarily halted so that the U.S. and South Korea could talk and coordinate over the recent exchange of artillery fire across the border. He said U.S. forces were at an increased security status for the exercise and "are remaining on an enhanced status as part of the exercise and, of course, to insure adequate deterrence on the peninsula."

He said the U.S. commander in South Korea decided to pause the exercise after consulting with South Korean military officials. He added that commanders needed to receive briefings about the gunfire situation to make sure that both the U.S. and South Korea had "a mutual understanding of what the situation is."

He said the U.S. is continuing to monitor the situation closely, adding that the U.S. calls on Pyongyang to "refrain from actions and rhetoric that threaten regional peace and stability."

North Korean leader Kim Jong Un on Friday declared his front-line troops in a "quasi-state of war" and ordered them to prepare for battle against South Korea in response to an exchange of artillery fire on the border.

The annual exercise began Monday and was slated to end next Friday.