* China to deepen supply-side structural reforms - Politburo
* Says will balance growth and risk controls in 2018
* Pledges to build 'long-term mechanism' for property market (Adds details, quotes)
BEIJING, Dec 8 (Reuters) - China will deepen structural reforms and curb risks while maintaining steady economic growth in 2018, the official Xinhua news agency said on Friday, as top leaders seek to prevent a destabilizing build-up of debt.
The government will balance the need to keep economic growth steady with efforts to push reforms and contain risks, Xinhua said, citing a statement released after a meeting of the Politburo, a top decision-making body of the ruling Communist Party.
"Promoting high-quality development will be the fundamental requirement for determining our thinking on development, formulating economic policies and implementing macro-control measures," Xinhua said.
President Xi Jinping said at a party congress in October that China will strive for higher quality, more efficient and fair growth.
Top leaders are due to map out an economic and reform agenda for 2018 during an annual Central Economic Work Conference later this month.
The government will deepen supply-side reforms next year to deal with excess factory capacity and structural problems, Xinhua said.
The Politburo also pledged to "prevent and resolve major risks to effectively control macroeconomic leverage ratios," Xinhua said.
The news agency also said the government aims to significantly cut emissions of major pollutants next year under a drive to fight pollution.
Authorities will also focus on speeding up property market reform and establish a long-term mechanism for the market in 2018, Xinhua added.
In the first nine months of this year, Chinas economy grew 6.9 percent from a year earlier. This was underpinned by stronger exports and sustained state spending, positioning China to exceed the governments growth target of around 6.5 percent this year.
Sources have told Reuters that Chinese leaders are likely to stick with that growth target for 2018, even as they ratchet up efforts to prevent a destabilizing build-up of debt. (Reporting by Beijing Monitoring Desk and Kevin Yao; Editing by Richard Borsuk)