North Korean leader Kim Jong-un inspected a large-scale military exercise of the country's flagship combined forces, its media reported Friday, as the defense chiefs of South Korea and the United States held their annual talks in Washington.

Kim "guided" the drill by the Korean People's Army (KPA) Large Combined Unit 526 and KPA Combined Unit 478, which include infantry, and mechanized and engineering units, the Korean Central News Agency (KCNA) said.

It was conducted in a "new manner" presented by Kim, added Pyongyang's official news agency, which did not reveal the specific timing and place.

The infantry "put the defense lines under control at a lightning speed through a bold attack in order to overcome various obstacles laid by engineering units and pave the way for mechanized units," according to the KCNA.

"Then units supporting the advancing forces conducted combat actions to destroy different kinds of obstacles." 

Kim was quoted as saying that the exercise was of much significance in implementing the nation's military and strategic policy.

"He instructed the KPA to frequently organize such a drill as the commanding officers and staff officers have to use their brains a lot when similar actual drills are staged between the two sides," the KCNA reported.

In Washington, meanwhile, South Korea and the U.S. agreed to postpone the transfer of wartime operational control (OPCON) of South Korean troops with no new date set, citing the North's growing military threats.

The deal came at the Security Consultative Meeting between South Korean Defense Minister Han Min-koo and his American counterpart, Chuck Hagel.  

The South was supposed to regain its wartime OPCON as of December 2015. (Yonhap)