Georginio Wijnaldum's opener just before the hour and James Milner's penalty secured a ninth consecutive win in all competitions for Klopp's men and moved them two points ahead of Manchester City, who have a game in hand, at the top of the table.
"It's really massive. We spoke a lot about this game, how special it is, how special the situation is for the opponent" said Klopp, who bemoaned the dry state of Cardiff's pitch under baking temperatures.
"It was not a game for playing around. It was a battle of will, who wants it more".
City travel to Manchester United on Wednesday in what appears the toughest hurdle left for the English champions to clear and deny Liverpool a first Premier League title in 29 years.