The Manhattan DA’s office won’t press charges against one of the motorcycle thugs believed to have terrorized a driver and his family after a wild chase on the West Side Highway, and argued against prosecuting a second biker before ultimately agreeing to, sources said Wednesday.

“F—!” the biker who was charged, Christopher Cruz, 28, of Passaic, NJ, said when he was swarmed by media as he left Manhattan Criminal Court on $1,500 cash bail, charged with reckless driving and unlawful imprisonment.

Cruz was caught on video allegedly starting the entire incident by brake-checking the victim’s black Range Rover during the Sunday biker rally — supposedly so that his companion bikers could take over the highway.

NYPD brass were hot on arresting Cruz despite zero evidence he’d committed an actual assault, sources told The Post.

“We arrested [Cruz] because of pressure from [police brass] to make an arrest in this case,” a second source said.

“It was completely against [the prosecutor’s] judgment. The case is weak. We needed much more investigation.”

The DA’s office relented because of pressure from the NYPD and widespread publicity about the case, a second source told The Post.

A statement from the DA’s top trial prosecutor, Karen Friedman-Agnifilo, confirmed that the office was proceeding with caution in building “the strongest cases possible” against the renegade bikers.

“Prematurely charging individuals with low-level crimes does not further the goals of the investigation, and could weaken the cases we expect to bring against the perpetrators of serious crimes,” Friedman-Agnifilo said in a written statement.

The biker who won’t be charged is Allen Edwards, a 43-year-old Queens man who is allegedly caught on video banging with his fist on the rear driver’s side window of victim Alexian Lien’s rear driver’s side window with his fist. He surrendered to cops Tuesday morning — but was released from the 33rd precinct without arrest, the sources said.

The failure to press charges against Edwards angered some cops. “The DA declined to prosecute. Look at [The Post’s] front page [Tuesday]. He’s there on the motorcycle right next to [Lien] after [Lien]got his ass kicked,” an angry law enforcement source said.

Video shows a man who might be Edwards pummeling the rear window of Lien’s Range Rover, near where his infant daughter was belted into a child seat, and Lien on the ground with Edwards next to him.

A second biker, Christopher Cruz, 28, of Passaic, N.J., who brake-checked the SUV — allegedly so that the bikes could take over the road was charged with endangering the welfare of a child and reckless driving.

“The case is weak. It was too early to tell if he committed the crimes he was charged with. It needed much more investigation,” the second source said.

Police, meanwhile, are zeroing in on two other suspects, including the one who slashed Lien, sending him to the hospital for stitches.

“They’re trying to ID two of the guys. One of them is the main guy. He’s the one that assaulted the victim. On the video, he was wearing the chrome helmet that has a logo of a bird,” a third source said late Tuesday.

A witness told police the biker in the chrome helmet pulled Lien out of the car, threw the terrified dad to the ground and stomped on his head.

The second suspect being sought also smashed windows on the SUV, the source added.

“He’s wearing orange and he hit the window of the SUV,” the source said.

Cops have gotten photos of hundreds of license plates from bridge and tunnel cameras and are trying to identify more of the bikers, who first swarmed Lien, his wife and child on the West Side Highway in HarlemSunday about 1:30 p.m.

But some of the plates turned out to be stolen or belong to different bikes, making it tougher to ID the motorcyclists.

The chase was caught on video by a helmet camera worn by one of the bikers — who later posted it on YouTube.

Early on in the chase, as Lien sped off to escape the pack, he ran over 26-year-old biker Jeremiah Mieses of Lawrence, Mass., whose spine was crushed. He remains hospitalized in a medically induced coma.