All Blacks to be without their leader in June
Read has been sidelined since November after suffering a nagging injury last season that was eventually diagnosed as a prolapsed lumbar disc.
The All Blacks initially estimated he would be out for four months but Hansen on Friday pushed out his recovery time, saying the inspirational No.8's long-term future could be jeopardised if he returned too early.
He was pessimistic about Read's chances of making New Zealand's three-Test home series against France in June.
"I don't think he'll be back until after the French series but that's not a fait accompli at this point," Hansen told Radio Sport.
"We'll just take our time. He knows his body and we can't afford to risk bringing him back too early and then damaging it again and being out for another six months and maybe even missing the World Cup.
"We'll just take it one day and one week at a time. It's an old cliche but it's what we've got to do."
Hansen was also doubtful about hooker Dane Coles' prospects of featuring against Les Bleus after he ruptured a ligament playing against France last November.
"Dane's having a few problems with his knee, he can't seem to straighten it out at the moment so the surgeon's put him in a brace at night to help him get full extension," he said.
"If that happens he'll make quick progress. Unlikely to be involved in June but after that [he] should be there."
New Zealand play France at Eden Park on June 9, then in Wellington on June 16 and Dunedin on June 23.