All Blacks captain Reed underwent back surgery at the end of last year after he slipped a disc and it was hoped he would have returned to Super Rugby for the Crusaders by now.
However, the 32-year-old has suffered a setback in his recovery and coach Steve Hansen says it is unlikely the skipper will be available for the three home Tests against France in June.
He told New Zealand's Radio Sport: "I don't think he'll be back until after the French series but that's not a fait accompli at this point. He knows his body and we can't afford to come back too early and damage it again, and miss another six months, and maybe even miss the World Cup.
"We'll just take it one day at a time and one week at a time."
New Zealand are also set to be without hooker Coles for the games against Les Bleus as he is also taking longer than expected to recover from a knee injury.
"Dane is having a few problems with his knee, too - he can't seem to straighten it," Hansen added. "He's gone back to the surgeon and the surgeon has put him back in a brace at night to try to help him get full extension.
"Once that happens he'll make progress pretty quickly. He is unlikely to be available for June."