Los Angeles FC defender Ciman had been training with the Belgian side in Russia in case Kompany or Vermaelen failed fitness tests.
Kompany injured his groin in a pre-tournament friendly against Portugal, while Barcelona's Vermaelen has been carrying a hamstring injury he suffered last month.
However coach Roberto Martinez said he was confident in the players at his disposal and was prepared to let Ciman go.
"Thomas Vermaelen has improved really well like we expected," head coach Martinez told reporters in Sochi, where the Group G match will take place. "He is not going to be involved in the game against Panama. I think medically he could be fit for the next two games."
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"With Vinny Kompany we are going to take until tomorrow to make the final call. But we are confident with his progress he has done since the Portugal game that he will be available to be involved in the third game of the group phase."
That means the Manchester City player could be fit to face some of his team mates in the group's big match, the game against England on June 28 in Kaliningrad.
In the meantime, Belgium's central defensive partnership will likely comprise either Tottenham Hotspur pair Jan Vertonghen and Toby Alderweireld, or Celtic's Dedryck Boyata.
The Belgians kick off their campaign against World Cup debutants Panama in Sochi on Monday. Group rivals England play Tunisia the same day.
(Reporting by Jack Tarrant; Editing by Amlan Chakraborty and Hugh Lawson)
