Rafael Nadal has extended his long injury layoff by another two months and will miss his country's Davis Cup semi-final against the United States.

"Nadal will not play in the next two months and will stop to rest and recover his knee," said an official statement from his home town of Manacor in Majorca, Spain.

"Among other things he won't be able to be at the disposal of the Spanish Davis Cup captain for the semi-finals tie against the USA," it said.

The French Open champion has been on the injury sidelines since his shock Wimbledon second round exit at the hands of unheralded Lukas Rosol in late June.

That meant he missed the London Olympics, the Masters series events at Toronto and Cincinnati as well as the US Open which is currently underway in New York and where he reached the final last year.

Torn tendon

Nadal has a torn tendon and inflammation in the left knee. The tear is being treated with medication, therapy and progressive rehabilitation, the player said.

"I really want to be back competing and enjoying the tennis tour but I have many years in front of me and my knee needs some rest," the 26-year-old said.

"I will be back when I have no pain and able to compete without fears."

Nadal said he felt better after meeting with doctors and happy that his condition had improved in the past weeks, enabling him to avoid surgery.

"I will continue to work with the plan my doctors have established to be able to compete as soon as possible in the right conditions," he said in the statement.

The former world number one has needed repeated injury layoffs over the last few years to rest his knees which take much of the strain that comes from his highly physical style of play.

There have been repeated fears expressed that the rest of his career could be jeopardised if the knee problems get any worse.

The winner of the Spain-USA Davis Cup semi-final, which will be held in Gijon from September 14-16, will face either Argentina or the Czech Republic in November's final.

A two-month layoff will mean that Nadal will miss the rest of the ATP regular tour season, but could conceivably play in the ATP Tour Finals which will be held in London November 5-11 as well as the Davis Cup final should Spain win through.