China is poised to take over operational control of a strategic deep-water Pakistani seaport that could serve as a vital economic hub for Beijing and perhaps a key military outpost, according to officials. The construction of the port, in the former fishing village of Gwadar in troubled Baluchistan province, was largely funded by China at a cost of about $200 million. It has been a commercial failure since it opened in 2007, because Pakistan never completed the road network to link the port to the rest of the country. Chinese control of the port would give it a foothold in...