North America’s largest commuter rail system is facing a potential shutdown as a deadline nears to reach a deal with unionized workers to avert a strike.

The Long Island Railroad that serves New York City’s eastern suburbs has been negotiating for months on a new contract with labor officials representing locomotive engineers, machinists, signalmen and other train workers.

A strike was temporarily averted in September when President Donald Trump’s administration agreed to help. Those efforts ended without a deal, giving both sides 60 days — ending 12:01 a.m. Saturday — to again try to resolve their differences before the union was legally allowed to go on strike or the agency could lock out workers.

Five labor unions representing about half the train system’s 7,000-person workforce warned this week that Saturday’s deadline was approaching.

The LIRR is the busiest commuter railroad in North America , carrying about 250,000 customers each weekday.…