Qatar and Kuwait are said to be lining up to invest $3.6bn (£2.4bn) in the flotation of the Agricultural Bank of China.
The share sale is set to be the world's biggest initial public offering (IPO).
News agencies Reuters and Dow Jones both reported that unnamed sources had confirmed the investment plans.
The Qatar Investment Authority would buy a $2.8bn stake making it the biggest single investor. Kuwait would put in another $500m-$1bn.
Agricultural Bank of China plans to sell a 14% stake on the Hong Kong and Shanghai stock exchanges for $23bn.
UK-based bank Standard Chartered is also expected to invest some $500m in the initial public offering.
Other likely investors include Singapore's sovereign wealth fund Temasek Holdings, Holland's Rabobank and Hong Kong businessman Li Ka Shing.