Crusader Kings II

[Ibn-Khaldun]

Monk's crusader state made me think about my current Byzantine game.

Catholics have declared Crusade to capture Jerusalem from the Fatimids. However, I have claims on it as well. So, I was wondering whether the crusade will end if I declare war on Fatimids and take Jerusalem before crusaders take it? As of now they are mainly fighting land battles (Fatimids haven't given the crusaders time to capture settlements) but it's obvious that Fatimids (who had to fight several civil wars from the start of the game) run out of manpower sooner than later.

So, will the crusade end if I take Jerusalem before the crusaders?