Mayor Bill de Blasio's upcoming $73.9 billion budget plan underestimates anticipated finances, according to the city's Independent Budget Office, which Friday forecast a tentative surplus.
The office said the upcoming fiscal year, which starts on July 1, is expected to end with a surplus of $833 million.
The numbers differ because mayors tend to rely on a more conservative forecasting model for how well the local and national economy will do.
In a written statement, de Blasio budget spokeswoman Amy Spitalnick said the administration's budget plan is "prudent in how we project revenue growth. We've seen the risks in neighboring states like New Jersey, which over-projected revenue and now face enormous deficits as a result."
Spitalnick was referring to recent news that N.J. Gov. Chris Christie is facing an $800 million budget deficit.
In New York, factors that could weaken the budget include a jump in interest rates, a weakening of tourism and the showdown in Washington over the budget or the debt ceiling.
Additionally the independent analysis, which is required by the city charter, warned that "numerous questions remain about details of the proposed labor pact" that was recently negotiated with the powerful teachers union, "details that could significantly alter estimates of just how much the settlement could cost in the coming years."
More than three weeks after the proposed deal was announced, enough question marks remain that the budget office said its analysts couldn't put a dollar figure on its cost.
"There are ample reasons for caution," said office spokesman Doug Turetsky.
The right-leaning Manhattan Institute's Nicole Gelinas, a critic of the mayor's budget, said: "This is so complex and difficult that they can't even try to estimate it."
The pact with the union, the 140,000-member United Federation of Teachers, includes back pay and, if ratified, would set a pattern for settling expired contracts with the rest of the city's nearly 300,000-total unionized workers. The administration has predicted the cost for all to exceed $17 billion, though they say the figure would be offset by factors like billions in health care savings.
The analysis also frets that the cost could rise if the police and firefighter unions balk at the pattern, and instead opt for arbitration.