The South African communications regulator may not approve a tie-up between mobile networks MTN and Indian Bharti Airtel, before the end of the year.
However, the deadline for the tie-up has been earmarked for the end of September.
The two networks have had extended talks twice before, and it is possible the deadline could be extended to October.
The deal would create the third biggest mobile network in the world, with the largest amount of subscribers.
Bharti Airtel has upped its offer to $14 billion for a 49 per cent stake in MTN and stock. Last year, it proposed $13 billion for the deal.