Roger Federer has announced his retirement from tennis, declaring next week's Laver Cup in London will be his farewell tournament.

The Swiss great, who has won 20 grand slams, becomes the first of the 'Big Three' on the men's tour to call it a day, with Rafael Nadal and Novak Djokovic still active.

Federer said he was making a "bittersweet decision", having battled knee injuries in the hope of returning to the tour.

Now 41 years old, Federer wrote in a statement on social media on Thursday: "As many of you know, the past three years have presented me with challenges in the form of injuries and surgeries.

"I've worked hard to return to full competitive form. But I also know my body's capacities and limits, and its message to me lately has been clear.

"I have played more than 1,500 matches over 24 years. Tennis has treated me more generously than I ever would have dreamt, and now I must recognise when it is time to end my competitive career.

"The Laver Cup next week in London will be my final ATP event. I will play more tennis in the future, of course, but just not in grand slams or on the tour."