China and South Korea have warned against the proliferation of weapons of mass destruction on the Korean Peninsula.
In a rare joint stand, the defence ministers of both countries said it could touch off an arms race in the region.
The visit to Seoul by China's Defence Minister, Chi Haotian, is the first of its kind and shows signs of a thawing of Cold War rivalries.
Chinese Defence Minister Chi Haotian flew into Seoul on Wednesday for a five-day visit.
The first visit to South Korea by a Chinese defence chief, it was seen by the hosts as a diplomatic coup over its rival North Korea.
China is one of North Korea's few allies.
The border between north and south is the last remaining Cold War frontier and there are fears on both sides that an arms race could destabilise the peninsula.
North Korea froze its suspect nuclear weapons programme under a 1994 accord with the United States.
But its missile, chemical and biological warfare capabilities have raised a new spate of alarm in the region.
South Korea's 2000 defence white paper, released in December, said North Korea had boosted its stockpile of chemical weapons fivefold over the years to five-thousand tons.
Pyongyang is also believed to have stockpiled anthrax and nine other types of biological weapons.
South Korea says it has no weapons of mass destruction on its soil, but some U-S experts believe the Seoul government possesses chemical weapons.
Upon his arrival, Chi Haotian met President Kim Dae-jung, another sign of the growing ties between China and South Korea.
While wanting more investment and trade with the South, Beijing so far has tried to keep its military contacts to a minimum to avoid offending North Korea.
This could all be changing.
"We are hoping to come up with an understanding on a goal that information exchange and military force can be used in peaceful ways in the coming years. The fact that this is happening between China and (South) Korea could encourage North Korea to pursue a much more peaceful foreign relations."
SUPER CAPTION: Park, Joon-Young, Professor of the department of political science and diplomacy
China opened diplomatic relations with South Korea in 1992.
Beijing is currently South Korea's third-largest trading partner, while South Korea is China's fifth largest.
Besides South Korea, Chi's visit is part of a tour of stops in Britain, Russia and Mongolia.