The sale of HSBC'S $9.4bn (£5.9bn) stake in the insurer Ping An is in doubt after Chinese authorities appeared to withdraw funding for part of the deal.
The China Development Bank is believed to have reneged on a promise to back Thailand's Charoen Pokphand Group, the chosen bidder for the stake.
According to reports in Asia, the CDB is concerned that the deal has become too complex.
Charoen Pokphand funded the first tranche of the acquisition itself, some 21 per cent of HSBC's stake.
It plans to pay for the remaining part with a mixture of cash and CDB financing.
However, the CDB is reported to be unhappy about the outside sources Charoen Pokphand has turned to for cash, raising doubts about its ability to buy the other 79 per cent of the stake.
Shares in Ping An fell 4 per cent in Hong Kong today, while HSBC also fell 1 per cent to 659.2p.
If the deal were to collapse it would be a significant setback to HSBC's restructuring plans. Britain's largest bank had been expected to book a $3bn profit on the deal.
Charoen Pokphand is owned by Thailand's richest man, Dhanin Chearavanont.
The company was the first multinational to invest in China's agri-business in 1979 and helped to modernise the Chinese farm sector.
HSBC declined to comment. CP and CDB were unavailable.