Updated

Analysts say the security of North Korea's missiles and nuclear, chemical and biological weapons would be a chief priority for China in the event of a major crisis involving its communist neighbor.

China is mum on any contingency plans, but questions are being raised with U.S. and North Korean tensions high and relations between Beijing and Pyongyang at a historic low. The scene along the China-North Korea border provides some clues.

Construction crews are at work on a six-lane highway to the border outside the small Chinese city of Ji'an along the Tumen River. The dearth of traffic and trade would suggest the highway is of little use, but it could facilitate the rapid movement of tanks and troops.