The outlook of Hong Kong's Aa1 rating was also lowered to stable from positive, reflecting the downgrading of China's perspectives.
China's credit fundamentals "remain consistent" with its Aa3 rating but "credit-positive structural reforms" under the new leadership, which are expected over time, "may not be sufficient over the course of the next 12-18 months to justify a rating upgrade," Moody's said in a statement.
Earlier this month Fitch downgraded China's local currency debt rating to A+ from AA-, while it affirmed the long-term foreign currency rating at A+.
Moody's praised China's strong central government finances and "exceptionally strong external payments position," as well as its continued robust economic growth.
But it said that "progress has been less than anticipated in the process of both reducing latent risks by making local government contingent liabilities more transparent and in reining in rapid credit growth."
It noted that the National Audit Office originally identified 10.7 trillion renminbi ($1.7 trillion) worth of local level liabilities at the end of 2010, or about 27% of GDP, of which RMB 6.7 trillion were on the local government budgetary balance sheets.
But it added that "uncertainty lingers over whether these figures represent the full extent of the contingent risks arising from local government financing vehicles."
VULNERABLE TO PROPERTY MARKET
Local government budgets depend increasingly on land sales, which makes the health of their finances vulnerable to volatility in the property market, which could raise the possibility of a need for greater central government support, Moody's said.
Another risk for China's economy in the agency's opinion is "the elevated growth in credit," which is "increasingly driven by lending by the non-bank, shadow banking system," according to the rating agency.
"While the total stock of shadow bank credit is currently not overly large and does not pose systemic risks, controlling such lending is beyond the scope of the People's Bank of China's policy instruments," it warned.
Downward pressure on China's rating could arise from a "significantly greater -than-anticipated" economic growth slowdown, worsening of government finances from a material crystallization of contingent liabilities or a rise in social unrest which would distract the authorities from carrying out sound economic and financial policies, the rating agency said.
Moody's raised China's ratings from A1 to Aa3 with a positive outlook in November 2010.
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