Mourinho regrets missing out on the chance to become a world champion after leaving Porto before they played in the Intercontinental Cup, a one-off match between the champions of Europe and South America to determine the worlds best club side.

Porto won the right to contest the match after Mourinho led them to Champions League victory in 2004 and they went on to claim the world title against Colombia's Once Caldas in Tokyo.

The tournament is now called the FIFA Club World Champion-ship and features the champions of every continent, with Brazil's Sao Paulo the current holders.

Whatever the format, Mourinho admits competing for a world title is a driving force behind his desire to win the Champions League for a second time.

He said: "I made one mistake in Porto. I left there when I was European champion.

"I could have won the Intercontinental Cup and I didn't because I left to come to Chelsea.

"So, if one day I win the Champions League again, I want to win the Intercontinental Cup and not give it to another manager to win.

"If Chelsea win the Cham-pions League I could not leave them because I don't want to miss out on becoming a world champion."

But to reach that stage Mourinho knows his side, who play their first fixture in this season's Champions League against Werder Bremen at Stamford Bridge on Tuesday, will have to overcome stiff opposition from Europe's top clubs.

He said: "For me a minimum of 10 clubs can win the Champions League and I think we are one of the 10 favourites.

"When you speak about the players Chelsea have signed it is correct to say we should be stronger and a contender for the competition.

"But Barcelona are the champions and have signed (Gianluca) Zambrotta and (Eidur) Gudjohnsen. Real Madrid have four or five top quality new players.

"Arsenal have many great players, Manchester United is a big team. Inter Milan have, in terms of numbers and quality, the best squad in the world at the moment.

"There is pressure for us to win but I can live with it. I don't say I like it or hate it. I just live with it."

Mourinho is an admirer of Werder, who finished second in the German league last season, and knows they will not be intimidated by the English champions.

He admitted the group, which also includes Barcelona and Bulgaria's Levski Sofia is certain to provide some tricky moments and said: "It could have been an easier draw. We want just to qualify, if possible first, but if not then second.

"Since I arrived at Chelsea, for three consecutive seasons we have had the European champions in our group. So it is never easy for us.

"They (Werder) are the best of third seeds. I don't think they are afraid of us. If you speak about a small team with inexperienced players, maybe they would be afraid.

"But Bremen are a good team in Germany with internationals who have played in the World Cup. They will not fear coming to play us.

"I think they respect us and they know they are in a very difficult group but they have ambitions to qualify."