An argument escalated into a physical fight on a Manhattan street Wednesday before one of the men stabbed the other with a knife, a law enforcement source said.

The source said a man stabbed another man in the chest in the area of 45th Street and Eighth Avenue just after 4:30 p.m. Wednesday.

The 30-year-old victim has a deep cut from the shoulder to the waist on the left side of his body, the source said. He's expected to survive.

Police taped off the scene as they investigated, disrupting pedestrian and vehicle traffic, especially for those trying to head to Port Authority bus terminal for the commute home.

Police had a suspect in custody at the Midtown South Precinct stationhouse.

-- Pei-Sze Cheng contributed to this report