"I won't be there. The priority is to be healthy and I have to stop," the world number one told sports daily AS on Monday.
"I can't be everywhere. After finishing the first part of the season I need to rest. I need 15 to 20 days to be in good shape for the second half of the season.
"I should have a check-up on my knees, and see how everything is going with the treatment we did, which is what has allowed me to carry on. The idea is to do what I did in 2010 to arrive the same or even better prepared for the US Open."
Nadal, who is defending his Wimbledon title in London at present, went on to criticise the hectic tennis schedule.
"The International Tennis Federation continues to get it wrong by insisting with the format and calendar for the Davis Cup," he said.
"There is zero consideration towards us, the players. If the best players don't attend, the competition loses prestige. The ITF should ask themselves why this happens."
Spain captain Albert Costa is due to name his Davis Cup team later on Monday for the World Group quarter-final to be played in Austin, Texas on July 8-10.
The US Open runs from August 29 to September 11.