Why are the State Police, whose relatively small 5,041-person force covers the state, patrolling in Staten Island when the city has the NYPD and its 35,000 cops? Is this another of Gov. Andrew Cuomo’s tweaks of archenemy Mayor Bill de Blasio?

“With the exception of 9/ll, this is an unprecedented deployment into an area that is the primary jurisdiction of the NYPD,” PBA president Patrick Lynch said of the two-trooper, 6 a.m.-to-4 p.m., seven-day-a-week patrols of the Staten Island Expressway.

Lynch said there’s a manpower issue, with cops being pulled off patrol to do terrorism work. As a union leader, hiring more cops is part of his agenda.

Cuomo says he directed the State Police “to partner” with the NYPD after an alert from Staten Island Assemb. Michael Cusick. In a statement released by the governor’s office, Cusick complained that the expressway’s HOV lanes have been “widely abused by vehicles with less than three passengers, due in no small part to a lack of enforcement.”

Cusick did not return phone calls as to why he had not sought assistance from the NYPD’s Highway Patrol, including Unit 5, which is based at 2330 Hylan Blvd. on Staten Island.

A Staten Island reader, noting the State Police presence, emailed: “They are supposed to be doing HOV enforcement only, but already they have started doing a little bit more here and there on S.I. highways. Is this goal of Mr. Cuomo to take over the NYC highways from the NYPD . . .? Who knows where it will go from there? Is the FDR next? Will Cuomo have his troopers stopping de Blasio?”

Over at the NYPD, which like other law enforcement entities is sensitive about its jurisdiction, no one is saying much about “partnering” with State Police. Neither Staten Island’s top police official, Assistant Chief Edward Delatorre, nor Lt. Joseph Bell of Highway Unit 5 returned phone calls.

NYPD Commissioner James O’Neill said only, “They let us know when they are patrolling.” He added, “I am good friends with George Beach,” who heads the State Police.

Asked how the partnering was going, State Police spokesman Beau Duffy said, “The State Police has a positive working relationship with the NYPD, and any rumors that this partnership has been anything but positive and productive are simply not true.”