Highlights - Brilliant Berdych stuns Federer (UK only)
Roger Federer is to work with coach Paul Annacone for a "test period" as the 16-time Grand Slam champion looks to get back to winning ways.
The Swiss will team up with Annacone as the American works out the remainder of his contract as men's head coach at the Lawn Tennis Association until November.
Federer has slipped to third in the rankings after losing in the quarter-finals of the last two Grand Slams.
Annacone is a former coach to Pete Sampras and Tim Henman.
"I've been looking to add someone to my team and I've decided to spend some days with Paul Annacone," Federer told his website.
"As Paul winds down his responsibilities working for the Lawn Tennis Association, we will explore our relationship through this test period.
"Paul will work alongside my existing team and I am excited to learn from his experiences."
The LTA announced in May that the 47-year-old Annacone would leave his post in November after three years with the organisation.
Following Federer's announcement on Monday, an LTA spokesperson said: "Any coach would relish the opportunity to work with one of the world's best tennis players.
"As outlined in Roger Federer's statement, Paul will do a number of days with Roger as he winds down his work with the LTA."
Federer, 28, has won Wimbledon six times, the US Open five times, the French Open once, and sealed his fourth Australian title earlier this year.
But his quarter-final defeat by Tomas Berdych at Wimbledon followed an exit
at the same stage of the French Open to Robin Soderling,
and he has subsequently dropped to number three in the world - his lowest ranking for seven years.
Federer has had several temporary associations with coaches in recent years, including Darren Cahill, Jose Higueras and Tony Roche.
He is next due in competitive action at the Rogers Cup in Toronto from 9 August, before the US Open gets under way on 30 August.