Mayor Bill de Blasio is proposing free, full-day early childhood education for all of New York City’s 3-year-olds by the fall of 2021.

De Blasio said Monday that the city hopes to launch a pilot of the “3-K” program next fall year at a cost of $36 million. But the state and federal governments would have to pitch in.

The cost would rise to $177 million when the program is fully in place.

The pilot program would focus on low-income districts in the South Bronx and Brownville, Brooklyn.

De Blasio has promoted universal pre-K as his administration’s signature achievement.

The administration says the city has more than tripled the number of 4-year-olds enrolled in free, full-day pre-K.

(AP)