The former Chelsea boss believes his fellow Portuguese Ronaldo "is certainly not the best" player in the world, instead claiming Sweden striker Ibrahimovic deserves the accolade after hitting 10 goals in Serie A this season.

Mourinho's comments are sure to fan the flames ahead of Inter's clash with United in the last 16 of the Champions League, which kicks off with the first leg at the San Siro on February 22.

"When I think how a player should be, names like Kaka, Ibrahimovic and (Lionel) Messi come to mind," Mourinho said.

"Messi is great and in two or three years' time he will win the Golden Ball (Ballon d'Or) award."

Ronaldo hit 42 goals as Manchester United won the Barclays Premier League and Champions League last season, but Mourinho remains unconvinced that he should be labelled the greatest on the planet.

"Ronaldo is a good player but he is certainly not the best," he said.

"He deserved the Golden Ball award because his team won the Champions League and the Premier League.

"But, for me, Ibrahimovic is the best."

Mourinho has also revealed he will let Adriano leave the San Siro in the transfer window if the Brazilian asks for a move.

The 26-year-old striker has endured a difficult season with the Nerazzurri and has been linked with a move to Chelsea or a possible return to Brazil.

Mourinho said: "Club president Massimo Moratti and I want him to stay. However, if he asked me to leave I would not oppose it.

"He has 10 years of football left to play."

Adriano, who is currently recovering from a thigh injury in Brazil, was left out of Inter's team for five games earlier this season after a disagreement with Mourinho.

Last season, Adriano's personal problems led to Inter loaning him to Sao Paulo for six months.

In Milan earlier this month, Inter denied media speculation that the player had turned up to training under the influence of alcohol.

Adriano has a reputation for having a party lifestyle.

"I don't know if he will be able to free himself from the tag that has been placed on him," said Mourinho.

"It certainly is difficult.

"I believe that a change of scenery could be positive for him.

"When I arrived, people said that a coaching change would be good for him.

"At the beginning it was but then Adriano's continuity was not 100%."

Mourinho believes Adriano is in need of someone who can guide him and he is not the person to do that.

"A player, in order to be a great professional, must never need his coach to control him," he said.

"Adriano needs a tutor, someone who is close to him, whether it's a friend, a team-mate or a family member.

"And this I do not like."

Adriano has scored just one goal for Inter in seven league appearances this season.

Meanwhile, Mourinho has once again played down media reports linking Chelsea striker Didier Drogba with a move to Inter.

Recent speculation has suggested the Ivory Coast international could be reunited with his former Chelsea mentor as part of an exchange deal that would see Adriano move in the opposite direction.

"I have never hidden my special relationship with Didier," said Mourinho.

"But I do not need another striker as I have Hernan Crespo, Julio Cruz, Mario Balotelli and Zlatan Ibrahimovic.

"But Drogba is more than a player for me, he is a part of me, an extension of the coach on the pitch."