Wilmots took the top job in 2012 and leads an exciting generation of Belgian talent into the FIFA World Cup in Brazil, starting later this month.
The 45-year-old has agreed to sign new terms which will take him up to 2018, but revealed in a press conference on Monday that he is yet to make the deal official.
"I have not yet signed," he said.
"I do not think there will be problems, and my signature will follow, but the deal is not yet quite official.
"As you know, there is an agreement for four years, but in football you never know."
Following friendly wins over Luxembourg and Sweden in the past week, Belgium have one more warm-up match, against Tunisia on Saturday, before flying out to Brazil where they will face Russia, South Korea and Algeria in Group H.
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