The New York City transit union has called for a partial strike against private bus companies, but says it will continue negotiating.

A strike deadline passed without a walkout when the contract between the Transport Workers Union and the state-run Metropolitan Transportation Authority expired at 12:01 a.m., local time Friday.

A top Transport Workers Union official, Roger Toussaint told a news conference that negotiations went far beyond the contract deadline because the union wants to work out a deal.

If talks fail and workers walk off the job, it would be the city's first subway and bus strike in 25 years.

New York Mayor Michael Bloomberg estimates a strike could cost the city $400 million a day.

Some information for this report provided by AP.