Mayor Bill de Blasio will unveil the city’s plan to rescue more than 90 low-performing schools in a speech Monday, according to sources, as calls for a detailed school-turnaround strategy have grown steadily louder during de Blasio’s 10 months in office.

The plan will cover 94 schools, including the roughly two-dozen struggling schools that are already part of an intensive-support program the city quietly launched around the start of the school year, according to a message sent Friday to principals in that program. The new initiative, dubbed “school renewal,” will invest more money in the schools and provide extra supports such as coaching and longer school days, according to people with knowledge of the plan who spoke on condition of anonymity. The city may take more drastic steps at schools that do not improve, the sources said, though it is unclear what could prompt the sanctions or what they might entail.

The expected announcement at the Coalition School for Social Change in East Harlem, first reported by the New York Daily News, arrives as de Blasio faces escalating criticism for his delay in introducing a school-improvement plan. De Blasio and his schools chief, Carmen Fariña, have repeatedly said they intend to prop up struggling schools rather than shutter them, but they have yet to say precisely how they will help those schools or if they will take more radical measures, such as replacing teachers or principals.

The city was required to submit improvement plans to the state for roughly 250 low-ranked schools this summer, but received an extension to this Friday. Nearly 40 of those schools must enact “whole-school reforms,” which the city has yet to describe.

Advocates have lambasted the administration’s “glacial pace,” as one put it, in addressing struggling schools, and the principal of a bottom-ranked school who recently resigned said he had lost faith in the city to help his school. On Friday, the New York Times editorial board assailed de Blasio’s “vague plan to give more ‘support’ to failing schools,” and urged the state to close the worst-off schools if the city fails to improve them.

In a statement last week, Department of Education spokeswoman Devora Kaye defended the time it has taken the administration to form a plan, saying it was “taking a thoughtful approach” that involved reinventing its “entire playbook.”

“The stakes couldn’t be higher for our students, and it’s worth the time to get it right,” she said.

The administration has already taken steps to prop up some troubled schools.

The 23 schools in the intensive-support program, known as the “School Achievement Initiative,” were assigned “redesign directors” and academic coaches. The city also appointed a superintendent to oversee the 13 high schools in that program.

The city also promised not to send new students mid-year to two of its lowest-ranked schools, Automotive High School and Boys and Girls High School, the Brooklyn school whose principal recently resigned. That policy change is part of the city’s plan for those schools, which have gone so long without making major improvements that the state labeled them “out of time.” The city has submitted multiple versions of that plan to the state, which sources at Boys and Girls said was necessary because state officials were not satisfied with it.

Fariña has also moved to restore some authority to the system’s superintendents, who will play a greater role in supporting schools. Last month, she announced a new school-rating system that she said would assist the city in propping up schools rather than “penalizing” them.