Belgium manager Marc Wilmots has admitted that his team's visit to Wales on June 12 will be their toughest Euro 2016 qualifier.
The Red Devils replaced Chris Coleman's charges at the top of Group B with five games left after Marouane Fellaini's strike secured a 1-0 win in Israel on Tuesday.
Wilmots told BBC Sport: "For us it's important to focus on winning each game.
"We were in Bosnia, we've been in Israel and coming up a match against Wales, which will be the hardest. After that we'll have an easier calendar."
Belgium and Wales, who drew 0-0 when they first met in November, are both unbeaten after playing five of their 10 Group B games.
