SHANGHAI, Aug. 21 -- INDIVIDUAL investors on China's mainland will have to wait for a while to directly trade Hong Kong shares though the country throw open the door this week.

The State Administration of Foreign Exchange said yesterday that it has approved a program to allow private investors to trade Hong Kong shares via accounts opened at the Tianjin branch of Bank of China on a trial basis.

In the first step, investors have to open account at the Tianjin branch of BOC. The service may be offered within a month once all procedure is available, said BOC International Holdings today.

BOC International will arrange the stock account trading and trust for investors on the mainland.

The trading will be expanded to other branches of BOC, the country's biggest foreign exchange bank, in the future, said the forex regulator.

For instance, Shanghai investors could open an account at the Shanghai branch of BOC, which will help smooth the following process and individual don't need to be present at the Tianjin branch personally.

However, the timeframe of the open-up and detailed procedure are not known yet, said BOC and BOC International.

The move, eyed as a big step forward in China's capital account opening, will help channel the country's mounting forex reserves and boost the Hong Kong stock market.

However, it may not blow the yuan-backed A share market though a short term psychological impact is possible, Jiang Jianrong, a Shenyin Wanguo Securities Co analyst said.

The expectation of an appreciating yuan and the sparse knowledge on Hong Kong market will be obstacles for a big forex outflow through the program.

The benchmark Shanghai Composite Index today rose 1.03 percent to 4,995.21.