Iniesta to miss Confederations Cup
"There is a strong chance of a relapse. He already had one in the Champions League final and we don't want another. He will leave now.
"He could be out for six to eight weeks but that is for Barca's medical team to decide. He needs a long period of recuperation."
Valencia midfielder Pablo Hernandez will replace Iniesta, according to a report on the Valencia website.
Iniesta picked up the injury at the beginning of May and returned for the 2-0 Champions League final win over Manchester United in Rome, where he aggravated the problem.
"It's a shame after the season we have just had, but there is no doubt it is the best decision for all concerned," said Iniesta.
On Sunday, Spain fly to Baku to play a friendly against Azerbaijan on Tuesday, before travelling on to South Africa.
The European champions, who have won six from six in qualifying for the 2010 World Cup, play their first Confederations Cup Group A match against New Zealand on June 14, and go on to face Iraq and then South Africa.