NEW YORK (AP) - Negotiations between New York City and the union that represents teachers in the nation's largest public school district returned to the bargaining table Thursday with hopes of hammering out a new contract.

NEW YORK (AP) Negotiations between New York City and the union that represents teachers in the nation's largest public school district returned to the bargaining table Thursday with hopes of hammering out a new contract.

The new multiyear deal, which could set a template for negotiations with more than 150 other unions working on expired contracts, could be announced by Mayor Bill de Blasio by late Thursday, according to people familiar with the negotiations.

The deal, which could be for as many as nine years, is expected to contain raises, some retroactive pay and substantial savings for the city on health care costs, according to a senior administration official and a labor official. They spoke on the condition of anonymity because they said they were not authorized to speak publicly about the deal until it is announced.

The United Federation of Teachers represents 100,000 teachers and other school employees who have been working on an expired contract since 2009. Union leaders have long pushed for substantial retroactive raises of up to $3.4 billion.

It was not immediately clear the size of the raises in the new deal or much health care savings would be achieved. The city has said recently it wants to save $1 billion a year from all of the city's unions.

If a deal is struck, it will end years of hostility between the teachers union and City Hall. De Blasio's predecessor, Michael Bloomberg, declined to grant any retroactive raises and often engaged in verbal clashes with the union's president, Michael Mulgrew.

Bloomberg, a Republican turned independent, long said the city could not afford the retroactive raises, which could total up to $8 billion. Many of the unions ended negotiations in recent years preferring to wait for a new mayor who may have warmer relations with unions; as a result, all of the city's unions' contracts had expired by the time Bloomberg left office.

De Blasio, a Democrat who took office in January, is a close ally of unions but has also expressed wariness about the city's ability to afford retroactive raises for all unions. Other labor leaders are anxiously eyeing the UFT negotiations believing it could establish baselines for future negotiations.

The teachers deal would also likely address several education issues, including teacher evaluations, the length of the school day and the ongoing debate over the 1,000 teachers who are still being paid even though their jobs have been eliminated.

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Associated Press writer Karen Matthews contributed to this report.