BEIJING — The Three Gorges Dam, the world’s largest hydroelectric project and a symbol of China’s confidence in risky technological solutions, is troubled by urgent pollution and geologic problems, a high-level government body acknowledged Thursday.

The statement came as technicians were certifying the very last of the dam’s array of generators as suitable for hydroelectric generation, the final step in a contentious 19-year effort to complete the project in defiance of domestic and international concerns over its safety as well as threats to the environment, displaced people, historical areas and natural beauty.

According to official figures, the venture cost China about $23 billion, but outside experts estimate it may have cost double that amount. The dam has been plagued by reports of floating archipelagoes of garbage, carpets of algae and landslides on the banks along the vast expanse of still water since the 600-foot-tall dam on the Yangtze River was completed in 2006. Critics also have complained that the government has fallen far short of its goals in helping to resettle the 1.4 million people displaced by the rising waters behind the dam.

China’s State Council, a coordinating body often likened to the United States president’s cabinet, said in a vague statement that the project suffered from a wide range of serious problems. “Although the Three Gorges project provides huge comprehensive benefits, urgent problems must be resolved regarding the smooth relocation of residents, ecological protection and geological disaster prevention,” the statement said.