Hi, this is Colum Murphy in Beijing, where Chinese officials are throwing a few sharp elbows in their running rivalry with the US.

China’s exports to developing markets have soared, opening indirect routes to the U.S. market that officials in Beijing worry may be closed under pressure from President Trump.

China said on Wednesday that the U.S. has undermined bilateral counter-narcotics cooperation by imposing tariffs on Chinese goods over fentanyl, calling on Washington to stop using the issue as a bargaining chip to "blackmail" the country.