The amount needed will also depend on the size of State capital offered for sale, said Dominic Scriven, Head of the Vietnam Business Forum's Capital Market Working Group.
According to Scriven, the Vietnamese stock market has not really attracted big and long-term investment capital from foreign investors as shown in market capitalisation that is quite small compared with other ASEAN countries.
Vietnamese market capitalisation is just one-fifth of the Philippines and one-tenth of Malaysia, he noted.
Scriven suggested that the Government speed up the equitisation process of State-owned enterprises (SOEs) and increase the proportion of State capital put up for sale, at least 30 to 40 percent of enterprise equity, to boost market liquidity in the market.
The working group pointed out that investors, particularly foreigners, lacked information on State enterprises' initial public offerings, which could leave them unprepared for such share sales.
They proposed that the authorities make up the list of groups, corporation and companies that would carry out IPOs, including timetables on a quarterly basis, for investors to have enough time to study and prepare plans for purchases.
Last month, the Ministry of Planning and Investment reported 100 SOEs equitised in the first 10 months of this year at a pace that Prime Minister Nguyen Tan Dung said was slower than expected.
PM Dung estimated the amount of State capital to be sold at US$56.4 billion and urged concerned agencies to accelerate this process to raise funds for development projects and improve SOEs' corporate governance.
On the issue of increasing foreign ownership in domestic companies, Scriven expressed disappointment over the delay in the State Securities Commission (SSC) plan to extend the time for lifting foreign ownership limits from 49 to 60 percent to October 2015.
Since the beginning of this year, the Vietnamese stock markets have attracted only US$150 million in foreign capital, which is far below the US$10-billion foreign direct investment target.
Scriven said the current 49-percent limit on foreign stakes in a domestic company relegated foreign investors to the purchase of shares worth a mere US$3.1 billion or only five percent of market capitalisation.
SSC Chairman Vu Bang explained that the commission has proposed the plan of raising the limit on foreign stakes to 60 percent in businesses where foreign investment was allowed by law, but the new regulation needed some legal changes that required more time and preparations.
Speculation on the easing of foreign stakes restrictions helped boost the stock market by 22 percent last year and 13 percent this year.