New York Lt. Gov. Mario Cuomo's former top aide pleaded guilty yesterday to three counts of a 20-count indictment that charged him with a payroll-padding scheme involving as much as $175,000.

William Cabin, 36, pleaded guilty to charges of grand larceny, forgery and offering a false instrument. He could face up to 18 years in state prison on the felony convictions.

The guilty pleas were part of an agreement with Albany County District Attorney Sol Greenburg, who said Cabin "will do state time" in prison.

Sentencing was set for Nov. 30, and Cabin was ordered held in jail.

At his hearing, Cabin said, "I did it, I know it was wrong and I have to face the consequences. It would be ridiculous for the people of New York to spend money for a lengthy procedure."

Cuomo fired Cabin last week from his $46,000-a-year post as executive director of the lieutenant governor's office. At a news conference Monday, Cuomo said he heard allegations against Cabin on Oct. 22 from other staff members and went immediately to Greenberg.

Cabin told the judge he had placed five fictitious people on the state payroll over a two-year period and had submitted travel vouchers for them.