BERLIN, Jan 16 - Bayern Munich and Germany midfielder Sebastian Deisler announced his retirement from football on Tuesday at the age of 27 because of a persistent knee injury.

Deisler, who missed last year's World Cup after undergoing knee surgery for the fifth time, announced the decision at a news conference held by Bayern on Tuesday.

"I no longer have any real faith in my knee," the player said. "In the long run it's been an ordeal.

"I can no longer play with the right level of enjoyment and I don't do anything by halves."

Blessed with speed, dribbling ability and an eye for a cross, Deisler was once widely seen as being the next great German player but fitness and psychological problems meant he was unable to fulfil his promise.

Germany coach Joachim Loew described the news as extremely regrettable for the German game.

"I'm very sorry that a player of his outstanding qualities should be forced to end his career like this," Loew said in a statement.

After making his Bundesliga debut as an 18-year-old with Borussia Moenchengladbach in 1998, Deisler played for Germany for the first time in 2000 and looked set for great things when he agreed to join Bayern from Hertha Berlin in 2002.

Injury kept him out of the 2002 World Cup, however, and continuing problems meant he hardly figured for Bayern in his first season.

HAPPY RETURN

He was sidelined for five months in the 2003-04 season while being treated for depression but he returned and looked a much happier man following the birth of his son, Raphael in 2004.

He was one of the outstanding players in the Germany side that reached the semi-finals of the Confederations Cup in 2005 and Juergen Klinsmann was hoping to play him on the right of midfield at the 2006 World Cup.

Another knee injury suffered in a training session last year dashed his hopes, though, and he also missed most of the first half of the current season.

He returned to make a handful of appearances as a substitute at the end of last year, including one quite brilliant display that earned Bayern a 2-1 win at Hamburg SV.

The stage appeared set for a return to his best this year before he finally decided enough was enough.

After showing so much patience with the player, Bayern were clearly disappointed by his decision to retire and manager Uli Hoeness held out hope of yet changing his mind.

"I don't understand his decision at all," Hoeness said at the same news conference on Tuesday.

"If he feels in condition at some time in the future he can always come back."

Deisler won 36 caps for Germany and scored three goals.

In the Bundesliga, he played 135 times and scored 18 goals, winning the league and Cup three times apiece with Bayern.