Both companies plan to introduce services for billed subscribers the day before the August 9 deadline set by the Nigerian Communications Commission, the regulator.
Nigeria is Africa's largest and perhaps most neglected telecoms market with fewer than one phone line for every 250 people. Nigerians hope GSM will end the telecoms drought inflicted on them by state telephone company Nitel.
As August 8 approaches, Econet and MTN are engaged in an intensifying marketing war, with new MTN billboards popping up daily in the commercial capital Lagos and Econet running full page newspaper advertisements promising "August is the month of change".
A source at Econet said the Zimbabwe-based company will launch with a 100 000 line capacity network despite the announcement from the communications minister that Nitel could supply Econet and MTN with only 5 000 voice interconnect channels each at any one time.
The 5 000 line limit will cause congestion when subscribers try to call Nitel lines but calls to other Econet and MTN subscribers will not be affected.
Econet will begin initially with billed customers and its pre-paid service is scheduled to be launched around October, the source said. Econet business development manager Kamel Okudo said last month that the company would have 500 000 lines by year end - more lines than Nitel's current number of land lines.
Econet, which has suffered severe financing problems since it bought its GSM licence for $285m, has announced it has sold 30% of the company to the Lagos, Delta and Akwa Ibom state governments.
First Bank of Nigeria has an option to convert money it lent Econet to help cover the cost of the GSM licence into a 20% stake in the company. In addition to the licence fee, Econet said last month it had spent $360m on equipment and will spend another $350m on vendor financing.