Race may have played a factor in the assault of a black man who was subsequently struck by a car on a Brooklyn parkway Sunday night, police said yesterday.

Police said a witness saw the victim backing away from two white perpetrators onto the Belt Parkway near Plum Beach in Sheepshead Bay, authorities said.

“It’s a possible bias crime, but again we don’t have all the facts,” the police commissioner, Raymond Kelly, said. The attack left the victim, identified as 28-year-old Michael Sandy, in critical condition and on a respirator.

Mr. Kelly said the victim had left his car running in a parking lot near Plum Beach when he got into a dispute of some kind with the two suspects. Police sources said the victim backed away from his assailants onto the Belt Parkway at Knapp Street, where he was hit by an oncoming car that was traveling in the passing lane. The car fled the scene. A female motorist who avoided hitting the victim witnessed the incident, police sources said.

The witness told police that one suspect fled the scene while the other dragged the victim off the roadway and rifled through his pockets. Then he appeared to search for something in the roadway, she told police.

In response to the attack, state Senator Carl Kruger said he would encourage park officials to shore up security by closing the area at dusk and installing security cameras. “It’s just a problem location,” Mr. Kruger, who represents part of southern Brooklyn, said. In 2002, a 55-year-old man was stabbed there after a sexual rendezvous, and in April 2005 the body of a Mexican gang leader was dumped there.

As of last night, police had no suspects in custody and declined to describe a motive in Sunday’s attack other than to say it was still being investigated.

Amid speculation of a bias attack, the police commissioner took the opportunity to defend recent allegations that implicate transit officers in racial profiling in a Park Slope subway station. The accusations, published in yesterday’s New York Post, allege that officers were ordered to target all black teenagers at the Seventh Avenue station of the F line in an effort to apprehend three youths suspected in a series of robberies.

Racial profiling goes against the department’s policy, Mr. Kelly said. “What happened was a pattern of robberies involving three young male blacks,” he said. “So it was specific to those three individuals.”