Standard & Poor's lowered its debt rating for China, the world's second-largest economy, in a Thursday release that cited a "prolonged period of strong credit growth".

S&P cut the rating one notch to A+, from AA-, and said the outlook for the new rating was "stable." The move follows a warning in June from the ratings company of a "real possibility" of a rate cut owing to the country's "fairly slow" progress in moving away from a credit-driven growth strategy.

"China's prolonged period of strong credit growth has increased its economic and financial risks," the company said.

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Moody's Investors Service lowered its own rating on China in May of this year to A1 from Aa3, citing the "expectation that China's financial strength will erode somewhat over the coming years, with economy-wide debt continuing to rise as potential growth slows."

"While ongoing progress on reforms is likely to transform the economy and financial system over time, it is not likely to prevent a further material rise in economy-wide debt, and the consequent increase in contingent liabilities for the government," Moody's said at the time.