The Bulgarian striker went down under pressure from Daniel Agger in the box after just 30 seconds, and World Cup final official Webb had no hesitation in pointing to the spot.
Ryan Giggs fired home what turned out to be the winnerfrom the spot as United won 1-0 over 10-man Liverpool in their FA Cup third-round clash at Old Trafford.
Berbatov told ITV1: "Of course it was a penalty. There was enough contact for me to lose my balance and people know I do not go to ground easily.
"I thought Liverpool put in a good performance and I thought their 'keeper Jose Reina was their best player and made some good saves, but we were the better side."
The other major talking point of Kenny Dalglish's first game back in charge of the Reds was the sending-off of captain Steven Gerrard just after the half-hour mark.
The midfielder left the ground as he launched himself into a tackle on Michael Carrick, with Webb taking his time to calm some raised tempers before showing the red card.
Goalscorer Giggs would not be drawn on the incident, saying: "I couldn't see it myself but the players' reactions tend to tell you a lot and the players round the ball were not too happy and once the decision is made you have to get on with it.
"That early goal helped us, as did the sending-off, but we had chances to finish off the game and you are a bit nervous when you don't take them.
"Defensively we looked good and we could have scored more today."