World number one Roger Federer made a surprise announcement on Tuesday when he revealed that Australian Tony Roche will be his new coach on a part-time basis.

Roche, who coached Ivan Lendl and Pat Rafter to the world number one spot and several Grand Slam titles, will team up with the Swiss for around ten weeks in 2005.

Federer, who won three of the four Grand Slam events last year, has been without a coach since parting with Swede Peter Lundgren in December 2003.

The arrangement with Roche is initially for one year, and Federer, who began 2005 with a 6-1, 6-1 win over David Ferrer in the Qatar Open on Monday, said the decision was a relief.

"It's good to know that there will be help there because I need someone to analyse and help improve my game," he said.

Roche had previously turned down the chance to coach Federer when the Swiss asked him in February 2004 because he did not want to travel too much.