China's top 21 securities brokerages said on Saturday that they would collectively invest at least 120 billion yuan ($19.3 billion or 12.39 billion pounds) to help stabilise the country's stock markets after a slump of nearly 30 percent since mid-June.
A flurry of official policy moves over the past week, including an interest rate cut and a relaxation of margin lending rules, has failed to arrest the sell-off.
A report in Saturday's Wall Street Journal said officials have decided to suspend new stock sales to help boost the beleaguered market. According to the publication, regulators and leadership figures held a meeting to discuss a new round of stabilization measures.
The move to suspend new sales could affect billions of dollars of initial public offerings in the pipeline, the Journal added.
The rout in China's highly leveraged stock market has become a major worry for global investors, who fear a meltdown could destabilise the world's second-largest economy at a time when growth is already slowing.
The brokerages met on Saturday in Beijing to discuss the market situation and expressed "full confidence" in the development of China's capital markets, a statement on the website of the Securities Association of China said.
"Twenty-one securities brokerages will jointly invest 15 percent of net assets as of the end of June, or no less than 120 billion yuan, in blue chip exchange traded funds," it said.
The brokerages will not sell off holdings as long as the Shanghai Composite Index is below 4,500 points, the statement said.
The SSEC index fell 5.8 percent on Friday to end at 3,684 points.
Listed securities companies among the 21 brokerages, along with their major shareholders, also would proactively buy back shares, the statement said.
Beijing has been struggling to find a policy formula to restore confidence in its stock markets.
After the market close on Friday, the China Securities Regulatory Commission (CSRC) said China would cut initial public offerings and capital raisings and support long-term investors entering the market to help stabilise prices.
The People's Bank of China (PBOC) also rolled over 250 billion yuan of medium-term loans to banks late on Friday to ensure adequate liquidity in the system.
Chinese stocks had more than doubled between November and mid-June, fuelled largely by retail investors using borrowed money.
Investors say constant tinkering with monetary policy and regulations to try to temper the stock market slide raises wider questions about whether China is ready to open up its capital markets and have more influence in the international financial system.
--CNBC contributed to this article.