NEW YORK (AP) — Mayor Bill de Blasio, his signature proposal suddenly taking unexpected criticism from an ally, strongly defended the city’s readiness to launch its massive pre-kindergarten program and stressed the unprecedented speed of expansion has not compromised safety.

De Blasio announced Thursday that 50,000 students have enrolled to begin pre-K for the first day of school on Sept. 4, just 3,000 shy of maximum capacity. But he quickly pivoted from leading the cheers to providing a vigorous rebuttal to the scathing report issued the day before by Comptroller Scott Stringer.