Offshore bondholders in Chinese property developer Kaisa have rejected an offer by the ailing group to extend the maturity of their debt and avoid a messy default next week, according to a letter to the company’s chair seen by the Financial Times.

The move could deepen a crisis at Kaisa, one of China’s most indebted developers, which has launched a fire sale of its assets in a bid to meet liabilities that include about $3bn of dollar bonds that will come due in the next 12 months.

A group claiming to represent more than 50 per cent of the investors in some of its most pressing debt — a $400m bond that will mature on December 7 — wrote to Kaisa on Tuesday to say that a proposal it made late last month to exchange the bonds was “unacceptable”, according to the letter.