Mayor Zohran Mamdani is floating a plan to delay payments into New York City’s municipal pension funds — his latest effort to stave off service cuts and a property tax increase as he grapples with a multibillion-dollar budget gap.

The plan, which the mayor’s team has presented to the administration of Gov. Kathy Hochul, could save the city at least $1 billion in the upcoming fiscal year, according to a person familiar with the discussions, and would be unlikely to affect pension payments for current retirees.

Mr. Mamdani’s team said it has yet to iron out the details. Any cost-cutting plan would most likely involve extending the deadline for the city to meet its long-term pension obligations beyond 2032, when it is scheduled to be up-to-date on its payments.

“While our administration has not yet put forward a specific proposal, we are actively assessing options for pension amortization,” Mr. Mamdani’s spokesman, Joe Calvello, said.

Similar proposals have drawn opposition from unions and fiscal watchdogs, with one leading budget expert warning they merely delay the city’s fiscal responsibility to avoid meaningful reductions in spending.

“The city is on a path to correct past fiscal mistakes and properly fund its pension obligations,” said Andrew Rein, president of the Citizens Budget Commission, a watchdog group. “It shouldn’t reverse course and stretch this out and make our children pay even more of our bills.”

One iteration of this proposal, presented this month by Julie Menin, speaker of the City Council, projected more than $1.2 billion in savings annually. An effort pushed unsuccessfully by former Mayor Eric Adams last year would have reduced costs by an estimated $1.3 billion in its first year.

Any delay to pension payments would need the approval of Ms. Hochul, who declined to comment.

Pension payments present a continuing liability for the city, which has a large unionized work force that has historically negotiated attractive retirement packages. The city’s total obligation to the five municipal pension systems for existing benefits, through 2032, amounts to $38.9 billion, according to data from the Citizens Budget Commission.

In 2013, under then-Mayor Michael R. Bloomberg and Gov. Andrew M. Cuomo, the city reformed its mandated pension payments following a drop in the assumed rate of return to 7 percent from 8 percent. That reduction meant the city had to pay more money upfront, creating a roughly $60 billion unfunded mandate. To address that, city and state leaders agreed to stretch out payments for future bills through 2032, at which point the added obligation was expected to be paid off.

The costs related to that change account for more than half of the city’s $10.5 billion pension expense this year, according to Ms. Menin’s office — a liability that is likely to grow.

Further delaying pension payments would significantly help Mr. Mamdani as he grapples with a $5.4 billion deficit through June 2027, which he has sought to reverse with risky and unpopular proposals, like raiding the city’s reserves and raising property taxes. He is also pushing Ms. Hochul to increase income taxes on wealthy residents, a proposal that is popular among Democratic state lawmakers but unlikely to get her backing. And he is asking her for more state aid to plug the hole as he navigates his first budget as mayor.

He is expecting to cut $1.3 billion from the current deficit by not expanding a housing voucher program and delaying, with Ms. Hochul’s blessing, a requirement to reduce school class sizes.

The plan backed by Mr. Adams, which Ms. Hochul tried to advance last year, ran into opposition from unions. Officials representing the pension fund for the United Federation of Teachers specifically raised flags about the Adams administration’s ability to carry out the plan, given concerns about the competency of the mayor, who was then under indictment, according to someone familiar with the matter.

Mr. Calvello said that the options being discussed were “distinct from the approach previously advanced by the Adams administration.”

Presidents of the city’s largest public-sector unions, Henry Garrido of District Council 37 and Michael Mulgrew of the teachers’ union, declined to comment on this development.

Mr. Rein urged city officials to consider other approaches to addressing the budget crisis.

“The city’s fiscal problem is a self-inflicted spending affordability crisis,” he said. “The best way to deal with that is to increase spending that works but eliminate spending that doesn’t improve New Yorkers’ life.”

A spokesman for Ms. Menin said she would review the mayor’s proposal when it reaches her desk. She is responsible for negotiating the city’s $127 billion budget with the mayor before it takes effect on July 1.

Mark Levine, the city’s comptroller, called Mr. Mamdani’s nascent proposal “a prudent step.”

“But the once-in-a-generation short-term savings this generates must be used wisely,” Mr. Levine added, “both to support the civil servants who pay into the system and to strengthen the city’s resilience against future fiscal and economic shocks, not as a way to avoid addressing our structural budget challenges.”