Mayor Bill de Blasio’s decision to provide six weeks of paid parental leave to the city’s 20,000 nonunion, managerial employees was welcome news to the city’s labor leaders and advocates of enlightened labor policies but it came with a cost: the Mayor’s Office unilaterally canceled a 2017 raise of 0.47 percent for some managers and reduced the number of leave days for its longest-serving city employees.

De Blasio’s executive order, which went into effect on Dec. 22, covers six weeks of paid leave at 100 percent of salary for parents who have or adopt a child or take one into foster care. Up to 12 weeks could be taken when combined with regular sick and vacation time.

The new policy does not extend to unionized city employees since paid leave must be negotiated under collective-bargaining rules. The mayor said he wants to begin negotiations as soon as possible.

UFT President Michael Mulgrew was among those who praised de Blasio’s initiative and said that many UFT members have long asked about parental leave.

“We have been trying for years to interest various city administrations in expanding parental leave, and finally have a willing partner on an issue that is very important to us,” said Mulgrew.

He said he looked forward to negotiations with the de Blasio administration for an appropriate way to expand parental benefits for UFT members. But he urged caution: “Everything has a price tag,” he said.

Mulgrew said the topic was moot in the past because the city was not open to the discussion. “Now we have an administration that wants to make this work so we will sit down with the city and discuss this,” he said. “Nothing can happen, obviously, until we bring back a proposal to the Delegate Assembly.”