Franky Vercauteren quit as Belgium coach following his team's 2-1 defeat to Armenia which ended their hopes of reaching the 2010 FIFA World Cup South Africa™ finals.
"I don't feel like continuing," Vercauteren said after the Group 5 match.
"I wanted to have 24 hours to think about it, but that would have achieved nothing. I prefer to stop straightaway," added the former Belgian playmaker, who was part of the side that reached the 1986 FIFA World Cup semi-finals.
Since the axing of previous coach Rene Vandereycken in April, Vercauteren had been keeping the seat warm until Dutch coach Dick Advocaat took over the reins on 1 January 2010.
I don't feel like continuing.
Belgium, who had lost 5-0 to European champions Spain on Saturday, are fourth in the group with seven points from seven matches, 14 points behind the Spanish.