Administrative issues prevented his appearance in the club's reserve fixture at Lincoln City during the week.
Stewart was due to take part in a totesport.com League East Division game at Sincil Bank on Tuesday afternoon but failed to secure international clearance in time to take his place in United's squad.
The out-of-contract midfielder has been on trial with Leeds for more than a fortnight and Simon Grayson hoped that an outing in Lincoln would allow him to reach a decision over whether to add Stewart to his squad for the remainder of the Championship season.
Stewart is a free agent and therefore eligible to join an English club outside FIFA's transfer window but United's intentions are unclear following his exclusion from Tuesday's fixture.
The former Manchester United trainee, who recently ended a short and ill-fated spell with Turkish club Genclerbirligi, could feature instead in next week's reserve game at Hull City, but Grayson admitted that the situation with Stewart was a secondary matter behind the priority of recruiting a new central midfielder before Saturday's Championship match at Swansea City.
Grayson said: "It was one of those situation where the clearance didn't come through in time for Michael to play so we'll wait and see what we do on that one. We've probably got more pressing matters to deal with in terms of who else I want to bring in first."
United's manager admitted last week that Stewart, 29, was a potentially viable recruit and a possible means of increasing the choice of central midfielders at Elland Road, a pool diminished this weekend by the loss of Bradley Johnson to suspension.