The fixture was initially scheduled to take place at the King Baudouin Stadium in the north-west of the Belgian capital but was cancelled after bomb attacks on the city's airport and metro system left at least 31 people dead and 270 more injured.
Portuguese officials subsequently offered to host the match in Leiria, a move that was agreed despite the Belgium coach's desire for the match to go ahead in Brussels.
Wilmots announced the team plan to show support for their home nation through a special shirt and by joining with the Portugal players for the national anthem.
"We will play with a shirt with a message in opposition to the attacks. The two teams will join for the national anthem tomorrow," he said.
Axel Witsel, who will captain Belgium for the match, added: "We all would have preferred to play in Belgium, but it is how it is, we have no choice. We have to live our lives, just like before.
"What happened in Belgium, it is difficult, shocking."
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