The country's gross domestic product grew at 6.2% in the second quarter, its slowest rate in almost three decades and lower than the 6.4% recorded last quarter, according to government figures released on Monday.
China's trading partners and financial markets are closely watching the health of the world's second-largest economy as the Sino-U.S. trade war gets longer and costlier, fuelling worries of a global recession.
"Economic conditions are still severe both at home and overseas, global economic growth is slowing down and the external instabilities and uncertainties are increasing", said bureau spokesman Mao Shengyong.
"China's growth could slow to 6% to 6.1% in the second half", said Nie Wen, an economist at Hwabao Trust.
Alongside GDP, China will also publish activity data for June including retail sales, industrial production and urban investment, which could give more clues on whether earlier support measures are starting to kick in, or if more policy easing is needed.
Retail sales for June rose 9.8%, eclipsing expectations for a slight pullback to 8.3%.
Washington sharply raised tariffs on $200bn of Chinese goods in May, increasing the strain on a struggling manufacturing sector and threatening to crush already-thin profit margins.
Analysts expect Beijing to unveil more stimulus measures to stabilize growth, including boosting infrastructure spending and possible interest rate cuts by the country's central bank, the People's Bank of China.
"The trade war is having a huge impact on the Chinese economy", said Edward Moya of OANDA.
Forecasters had expected China's economy to rebound in late 2018 but pushed back that target after President Donald Trump hiked USA tariffs on Chinese imports to pressure Beijing over its efforts to develop advanced technologies.
Alarms bell ring whenever there are reports that China's economy is slowing down.
China's economic growth rate slowed from 6.4% in the first three months of the year, by growing to just 6.2%. The US Federal Reserve has also signaled it may lower interest rates. Companies also invested more heavily than expected in things like land and equipment, so-called fixed assets, which rose by 5.8 percent in the first six months compared to the same period in 2018. China's June industrial output climbed 6.3% from a year earlier, beating a 5.2% forecast.
Sales of big-ticket items such as cars have not held up, though, with sales down 12.4% in the first half of the year, according to the China Association of Automobile Manufacturers. But new home sales shrank for a second month.
And this one chart shows why slowdown in the world's second largest economy, behind the United States, is unsafe for the rest of the globe. It rose 10.1% from a year earlier, accelerating from a 9.5% gain in May but still slower than in April, Reuters calculated.
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