The so-called XO machine is being pioneered by Nicholas Negroponte, who launched the project at the Massachusetts Institute of Technology’s Media Lab in 2004.
Test machines are expected to reach children in February as the project builds towards a more formal launch.
Mr Negroponte told the Associated Press news agency that three more African countries might sign on in the next two weeks.
The laptop is powered by a 366-megahertz processor from Advanced Micro Devices and has built-in wireless networking.
It has no hard disk drive and instead uses 512 MB of flash memory, and has two USB ports to which more storage could be attached.