Portside

Mayor Bill de Blasio is set to announce on Wednesday a $15-an-hour minimum wage for New York City’s public work force that city officials said would be among the highest of its kind in the country.

Under the mayor’s plan, which matches a similar increase for state employees enacted by Gov. Andrew M. Cuomo last year, about 50,000 city workers — including crossing guards, prekindergarten teachers, custodial workers and others — would see their pay reach the $15-an-hour level by the end of 2018.

Mr. de Blasio, a Democrat who is starting his third year as mayor, has pledged to refocus his administration on a core liberal mission, and the wage announcement, described by city officials on Tuesday evening, is sure to win praise from his left-leaning base.

The majority of the city’s 300,000 employees already earn $15 an hour or more, officials said. Mr. de Blasio’s plan would affect about 20,000 unionized workers, mostly represented by District Council 37, and 30,000 employees of outside organizations — like day-care providers — whose services are paid for by the city.

The increase in wages is expected to cost an additional $238 million over the next five years, concerning some fiscal experts. “The mayor has been lucky so far with the economy,” said Nicole Gelinas of the Manhattan Institute. “If a recession comes, higher wages will have to mean more layoffs.”

The mayor’s move comes in the same week that Mr. Cuomo, a Democrat, said he would provide a $15-an-hour minimum wage to about 28,000 state university workers. In November, the governor made New York the first state to set a $15 minimum wage for public employees; he also took steps to secure $15 an hour for workers at fast-food chain restaurants in the state.

Unlike the governor, Mr. de Blasio does not have unilateral power to raise city employees’ wages. To enact his plan, Mr. de Blasio has directed his team to amend existing contracts with the relevant municipal unions, and to rewrite contracts with the affected nonprofit groups. The new policy was reported on Tuesday evening by The Daily News.

The $15 minimum wage has become a rallying cry for liberal activists across the country who have urged state and city governments to raise workers’ pay after years of wage stagnation.

The mayor has sought other ways to provide more generous benefits. Late last month, Mr. de Blasio said the city would begin offering six weeks of paid parental leave to 20,000 city employees.

“We know that nothing does more to lift up working families and move our economy forward than raising wages, and the city is leading by example by doing just that,” Mr. de Blasio said in a statement.

The mayor is expected to announce his plan at an event on Wednesday afternoon at the headquarters of District Council 37, the city’s largest municipal union, in Lower Manhattan.