MTN, which was scheduled to make an important announcement this morning, has instead extended its negotiations with India's Bharti.
The company had called a press conference for today, at which it was widely expected to make an announcement on the talks, which have been continuiing since 25 May.
MTN and Bharti announced at that time that they had agreed to talk exclusively to one another regarding a potential merger.
The exclusivity period has already been extended once and has now been extended again, until 30 September.
MTN says in a statement today that "discussions between the parties regarding the potential transaction continue to progress satisfactorily and the parties have accordingly agreed to extend the exclusivity period until 30 September 2009.
"No decision or agreement to acquire any shares or implement the potential transaction outlined above has yet been made by the boards of either MTN or Bharti and the discussions may or may not lead to any transaction," it states.