STILIAN PETROV has warned Celtic they'll have their work cut out keeping his countryman Dimitar Berbatov quiet tomorrow night at Old Trafford.

The former Hoops midfielder is a massive fan of his Bulgarian team-mate and has identified him as a big danger to Gordon Strachan's team ahead of their Champions League showdown with Manchester United.

With Sir Alex Ferguson set to start with Berbatov, Wayne Rooney, Carlos Tevez and Cristiano Ronaldo tomorrow night, many fear they could prove too hot for the Hoops.

Berbatov, a £32m signing from Spurs, has added a new dimension to United's attacking play and netted his first goal at Old Trafford during their 4-0 victory over West Brom.

And Petrov says he could give his former club serious problems as they go head to head once again.

"Dimitar is a world class player," said the Aston Villa man. "He is more than capable of hurting the best teams in the world. That is why Manchester United paid so much money to sign him this season.

"There were a lot of huge clubs after him and you only have to see how he has performed since signing for United, and even before that at Spurs, to realise just how fantastic a footballer he is.

Stan added: "He is a very ambitious person and is now at one of the biggest clubs in the world. I've played beside him for Bulgaria and I appreciate just what he offers a team.

"When he has the ball in the final third, you know he can do something special to create a goal. So he is someone Celtic will have to pay close attention to tomorrow night."

The problem for Celtic is that there are another five or six United players who are equally as dangerous in and around the penalty area.

Wayne Rooney has netted eight goals in his last six games for club and country, Argentine internationalist Tevez is still considered one of the most lethal finishers in the business and Ronaldo is back on top form again.

Petrov said: "United have excellent attacking players. That is why they are such a fantastic team. They are strong in defence and very good in midfield as well. But when you have Rooney, Ronaldo, Tevez and Berbatov, not to mention midfielders such as Ryan Giggs and Nani, then there are so many creative players who can all score and create goals.

"That is the reason they won the Champions League last season and the Premiership. And they have improved since then by signing the likes of Dimitar. He has made them even better."

Petrov, though, hopes Celtic can somehow come up with something special to take at least a point from the game.

He said: "It is going to be extremely difficult for Celtic. It is hard for any team playing against United and going to Old Trafford is tougher again.

"But Celtic have good players, such as Aiden McGeady, and they will be cheered on by a large and vocal support. So you never know what could happen but it will be especially difficult for them."

Ominously for Celtic, Berbatov appears to be clicking into gear with Rooney, and he believes that their fledgling partnership is about to blossom.

Rooney is on fire at the moment, and Berbatov said: "I think he's enjoying his game and that's not only good for him, it's good for everybody, especially the fans.

"Our partnership is improving. We're working at it on the training ground, trying to understand each other without even looking. Sometimes it works - Saturday's result proves it and we want to take that forward. It was a nice goal for me to score at the weekend, and I was really delighted to score in front of the home crowd. Hopefully there will be more to come."

Hoops boss Gordon Strachan will have noted how, from a decent looking position of 0-0 at half-time, the Baggies were battered with a second half onslaught, just when they looked to be on course to maybe snatch something.

"There are often games like that," Berbatov mused. "In the first half you try hard to score but it doesn't work.

"Then at half-time, you have some good words from the manager - he tells you what to do exactly and what the weak points of the opposition are. You try to listen, we did listen and we scored four goals."