China is likely to unveil rules this month for a plan to channel Hong Kong-based yuan deposits to mainland equities but may delay the implementation to shield the market from overheating, sources said yesterday.

The country's securities regulator may pick about 10 brokerages and fund firms to participate in the program on a trial basis, according to people familiar with the matter.

The combined investment quota may reach 30 billion yuan (US$4.5 billion), up from an originally planned 20 billion yuan, to meet increasing demand from institutions for the new business, according to the sources.

However, the initiative won't likely be put into operation until at least December as the mainland stock market is heading north and money managers need time to set up efficient risk-management systems, the people said.

"Regulators don't think they should hurry to let the project run as mainland stocks have been rising of late," said a Shanghai-based securities executive, who was briefed on the matter. "Previously, they were eager to shore up liquidity; but they are somewhat concerned about overheating now."

The Shanghai Composite Index has jumped 14.9 percent this month and 27.6 percent from its 2010 low on July 5 after lagging behind tallies in other emerging markets and as the yuan's appreciation enticed capital inflows.

Still, the key mainland gauge is down 7 percent this year after the central government tightened measures to clamp down on property speculation and reduced the yearly new loan quota by nearly a quarter.

The new program, dubbed "mini-QFII," will complement the existing Qualified Foreign Institutional Investor project, which lets overseas institutions trade yuan-denominated equities in Shanghai and Shenzhen.

Just like the QFII scheme, institutions wanting to participate in "mini-QFII" will be required to apply for investment quotas.

About 30 mainland brokerages and fund houses now have subsidiaries in Hong Kong.

"Apart from helping the domestic stock market, 'mini-QFII' will also work to boost the international status of the Chinese yuan," said a Shenzhen-based fund manager involved in the program.

"Many asset managers hope to gain presence in it as quickly as possible as it could be lucrative in the future."