ChemChina is facing a funding gap of $15 billion for its purchase of Syngenta, the Chinese news service Caixin has reported. Citing people close to the negotiations and private documents, the news agency said the current financing structure indicates uncertainties over who will meet the shortfall needed to acquire all of Syngenta’s shares.

The Chinese company is borrowing heavily to finance the purchase, and its debt ratio is already at 80%, according to public company documents. It plans to raise $50.4 billion for the acquisition, using the funds to buy all of Syngenta’s shares, which are valued at $43 billion, support a reorganization of the assets and pay for associated expenses.

The offer made in March indicated a commitment by bank consortia to provide the initial financing needed to complete the acquisition. However, investors have said it would be difficult to raise capital if there was not some indication of support from the Chinese government, which has so far been lacking. The country’s state-owned banks are also notably absent from the list of creditors.

According to one US analyst, worries about the debt risk have always been present, despite the commitment by banks, but in the past had taken a back seat to concerns that the deal may be blocked in the US. However, the Committee on Foreign Investment in the United States (CFIUS) cleared the takeover of the Swiss seeds giant in August.

Refuting the Caixin story, a Syngenta spokeswoman told the Reuters news agency that bridge financing is “committed and irrevocable” and that ChemChina is proceeding with its refinancing strategy. ChemChina filed for European regulatory approval on Sep. 23, and a decision is provisionally expected by Oct. 28. The Beijing-based group has extended its main offer period for a third time, until Nov. 8 currently.