The 100,000 free childcare seats the city promise New York public school parents won't become entirely available until December, Mayor Bill de Blasio announced Tuesday. 

Only 30,000 Learning Bridges childcare slots will be available when schools reopen on Sept. 21 and only 70,000 in October, de Blasio said. 

"Starting something from scratch is a huge endeavor," de Blasio said. "The goal was 100,000 and we'll get to 100,000." 

De Blasio announced in July that the city would provide childcare options to help parents of blended learning students rejoin the workforce in the fall.

"So many parents have also said that they can't make it work if they don't get more childcare," de Blasio said in July. "The goal will be to start by serving 100,000 kids and giving those families, those parents that balance in their life, that relief, that support, but then we aim to go farther."

Council Members Brad Lander and Ben Kallos — who said in July need could be as high as 533,000 seats — both said they were disappointed Learning Bridges would reach less than a third of those initially projected. 

“It is a gigantic task to create a whole new program to serve tens of thousands of families, especially as the child care industry craters from lack of support, and I’m glad the administration has committed to doing so," Lander said. 

"But on the other hand, if you are a teacher who had to be at work today and had no child care options, it's too little too late."

Kallos, less reserved in his criticism, said he was extremely frustrated that City Hall never responsed to his repeated offers to help locate childcare facilities. 

"This is nowhere near enough," Kallos said. "I should be surprised, but I'm not.  I'm angry because all these families were counting on us. I don't know how we're going to open [schools] this month at this point.  

The Education Committee member also argued the lack of childcare would only worsen problems sure to arise from the DOE's complicated blended learning schedule. 

"Parents are forced to chose between having a job and taking care of their kids because, right now, you cannot do both," Kallos said. "Where are the parents, children and families supposed to be?"

On Tuesday, two days before classrooms were initially slated to reopen, Youth Services Deputy Commissioner Susan Haskell updated New Yorkers on the program, which will provide childcare and meals on remote learning days for students from preschool to grade eight.

Preschoolers' days will include play, social skills development and early learning while lower and middle school students will get remote learning support, art classes and exercise time. 

Parents who have expressed interest on the DOE website will be automatically enrolled and others can apply here.

"We want to assure parents," Haskell said. "Activities will be offered in a safe and welcoming environment."

During Tuesday's press conference, DOE Chancellor Richard Carranza also informed parents about 2,800 out of 64,550 public school classrooms were deemed too unsafe to reopen. 

"There are little things that need to be done," Carranza said. "But keeping our promise, we said everyone would have functioning ventilation."