Spokesman Jim Gannon of Transport Workers Union Local 100 said negotiations with the Metropolitan Transportation Authority continued on Monday with talks centering on station workers. The contract expired at midnight.
Negotiators working on the main contract issues will resume talks on Tuesday.
The two sides are trying to find common ground for a new three-year collective bargaining agreement covering subway and bus workers.
The union is demanding raises to counter the rising cost of living. The MTA is trying to holding to hold down payroll costs as part of statewide budget cuts.
Past contract negotiations have sometimes turned ugly. In December 2005 transit workers struck for three days and stranded millions of commuters.
Get Eyewitness News Delivered