De Bock, 25, has only made six appearances for his current club in Belgium this season, but had been at their winter training camp in Spain over the last few days.
Leeds look set to add to their January signings, having already brought in Finnish defender Aapo Halme and Japanese midfielder Yosuke Ideguchi.
United are hoping to bolster their squad for the second half of the campaign as they look to maintain a promotion challenge, with the side currently sat sixth in the table and in play-off contention.