"Defeat produces doubt and it's now up to us to provide
the right answers.
"The result has left me a little unsure but it might
help to put everyone back on the right track."
But Lemerre was eager to point out that his side had been missing their star player, Zinedine Zidane, and their first-choice striker, Thierry Henry, for the game at the Stade de France.
"The Belgians did play well, but with them (Zidane and
Henry) unavailable I was deprived of two options in my
strategy," he argued.
"I would have made more changes during the match but I couldn't."
Arsenal midfielder Patrick Vieira also defended the French side.
"Some say we concede more goals, meaning the defence is weaker," he said.
"But we also score more goals and that proves the ball is pushed through much faster."
France have one more friendly, against co-hosts South
Korea in Suwon on 26 May, before kicking off the World Cup against Senegal.
"As world champions, we have a duty to excel," Lemerre said.
"From the first second of the opening match, we will have a duty to get the
"The opening match is a game which can't be compared to any
"History teaches us that it can be very tricky sometimes. So it would be great if we could impose ourselves."