Earlier reports had suggested that the bank's listing in Hong Kong would come before the end of March.
However, regulators may be delaying the IPO while they decide how to structure the share sale to allow for a listing on the Shanghai Stock Exchange, reports in the state-run China Securities Journal and Hong Kong newspapers said on Wednesday.
Wang Zhaowen, the bank's spokesman in Beijing, would not comment on the timing of the widely anticipated listing, the second by one of China's large state-owned banks.
Wang said he had not heard of the listing plan being delayed until June, but he would not say if it would happen by the end of March.
According to the China Securities Journal, the bank has already submitted a request for IPOs in Hong Kong and Shanghai to China's cabinet, the State Council, for approval.
The Hong Kong listing would come by the end of May, and the Shanghai listing by the end of July, it said.
The listings will not come simultaneously, it said, because share offerings in the mainland have been put on hold while markets carry out shareholding reforms.
The South China Morning Post in Hong Kong reported on Wednesday that the bank could submit a preliminary application to the Hong Kong Stock Exchange for a US$8 billion IPO as soon as this week. It did not name its sources.
If the Hong Kong bourse "fast-tracks" its review of the bank, it could launch the share sale in May, it said.
China is restructuring its state-owned banks, encouraging foreign investment and allowing them to sell shares as it cleans up an industry notorious for lending scandals and huge levels of bad debt.