The Reds are currently eight points ahead of United.
He said: “When the gap is 20 points, then I will relax.
“With this small difference all I can say is we must keep going and not think about what other teams are doing.
“We were aware before we played West Brom that Manchester United had lost, but it was not something that we allowed to affect how we played.
“If you spend the whole time with a calculator considering what others are doing, it will drive you crazy.
“United have a game in hand and the ability to make up points in just two other games is not that difficult for them.
“So I don’t think I will be celebrating until the gap is 20 points.”