Ivanovic out of Serbia qualifiers
"I asked Chelsea to let me come to Belgrade for a couple of days to spend some time with the team but I knew straight away I would be unfit to play," he told the Serbian Football Association's website on Tuesday.
"There is a very slim chance I might recover for the Slovenia game but it is unlikely because the verdict is I could be out of action for up to six weeks."
Ivanovic was injured in Chelsea's 6-0 Premier League win at Wigan Athletic earlier this month. Antonio Rukavina or Pavle Ninkov could stand in for Serbia's first-choice right-back.
Serbia's other Group C rivals are Italy, Estonia and Northern Ireland.