We are getting better with every game
Tunisia coach Ammar Souayah
The Carthage Eagles went a goal down within the first 10 minutes, but bounced back thanks to a spectacular free-kick from Raouf Bouzaine.
Shortly afterwards they should have had a penalty after a clumsy Belgium tackle inside the area, but it was unseen by the referee.
And Kaies Ghodbane saw a late shot from 20 yards sail just over the bar.
"I am generally satisfied," Souayah confirmed.
"The players showed great spirit and great character."
Bouzaine's goal was only Tunisia's second in 10 international matches, but Souayah insisted that overall his side could have had more.
"It was a relatively balanced match but we deserved the better," he said.
The result leaves the Carthage Eagles bottom of the group and needing a good win over leaders Japan to have any hope of qualifying for the next round.
But Souayah said he was still happy with Tunisia's World Cup so far.
"I challenge any team to have known each other for only a month to be in the position we are in the competition," he said.
And he retained optimism despite the precarious position they now find themselves in.
"We are getting better with every game," he added.
"Our hopes are high and our confidence is still intact going into the game against Japan.
But he acknowledged the task would be very hard.
"We don't really have much of a chance against Japan, they are at home with their own crowd, they have a very good team and it's going to be very difficult," he conceded.