A recent report by Republican staff members in the U.S. Senate warns that China, because of its deepening economic ties with North Korea as well as its ancient claims on Korean land, could attempt to "manage, and conceivably block," the eventual unification of the two Koreas, if ever the Kim family falls from power in Pyongyang.

The report was released last month with little fanfare, but North Korea watchers say it gives voice to an increasingly popular but still-sensitive sentiment: that China will ultimately try to prevent the South from absorbing the North, the long assumed postcollapse scenario.

Such a situation is well down the road, experts say, but it resonates at a time when China is playing an aggressive role elsewhere in the region, staking claim to much of the South China Sea and to islands administered by Japan.