South Korea and the United States on Tuesday began a preliminary training in the runup to next week's annual summertime military exercise amid the North's warning it will take a toll on inter-Korean relations, sources said.

The four-day crisis management staff training is aimed at checking the military's response to unexpected situations before a war breaks out. It will be followed by the main computer-simulated Combined Command Post Training scheduled for Aug. 16-26, according to the sources.

The two countries have decided to push ahead with the drills as planned, albeit in a scaled-back manner due to the pandemic, despite North Korea's warning the maneuvers will dampen the budding conciliatory mood between the two Koreas.

Pyongyang has long railed against such exercises, denouncing them as a rehearsal for invasion.

Whether and how to conduct the summertime exercise have drawn keen attention, particularly after Kim Yo-jong, the sister of North Korean leader Kim Jong-un, said it could undermine efforts to improve inter-Korean ties following the restoration of the long-severed cross-border communication lines late last month.

With the launch of the preliminary drills, Kim Yo-jong issued another statement expressing "strong regrets" over the South's decision to stage the exercise, calling it an "act of self-destruction" that will destabilize the security situation on the Korean Peninsula.

"We will accelerate our push to strengthen preemptive strikes capabilities ... in response to growing military threats from the US," she said in the statement carried by the North's official Korean Central News Agency on Tuesday.

According to Rep. Shin Won-sik of the main opposition People Power Party, the upcoming drills will involve only 30 percent of the size of the reinforcement troops mobilized during the springtime exercise in March.

The augmented size this spring was already just a quarter of the normal level, Shin said.

The defense ministry has said it will decide how to stage the drills with various factors -- including the COVID-19 pandemic, the allies' combined readiness posture and the diplomatic efforts for the denuclearization of North Korea -- taken into consideration. (Yonhap)