SHANGHAI — On the surface, China’s economy is humming along smoothly. It’s the numbers behind the numbers that point to mounting challenges for the world’s other economic superpower.

The Chinese government on Monday reported that the economy grew 6.7 percent in the three months that ended in June compared with a year ago. That is pretty close to the rate that China has reported quarter after quarter over the past two and a half years. The pace puts it comfortably within its target of achieving growth of around 6.5 percent for the full year.

Those figures belie warning signs elsewhere. More detailed data show weakening investment in infrastructure and less exuberant spending by China’s usually ebullient consumers. Private businesses complain that government efforts to tame debt have made it hard for them to borrow money. A tiny but growing number of Chinese companies have defaulted on their loans. The currency has lost some of its value. Chinese stocks are in bear market territory.

It may just get tougher from here.

The United States has started a trade conflict with China, and by this autumn it could widen the conflict by hitting another $200 billion in Chinese goods with tariffs. While the Chinese have made progress diversifying their economy, the country still relies heavily on making and exporting toys, clothes, car parts and other goods to the United States and elsewhere.