NEWARK, N.J. (AP) _ Former U.S. Sen. Harrison Williams Jr., the highest-ranking official to be convicted in the FBI's Abscam bribery-conspiracy investigation, just wants to be left alone for a while, a neighbor says.

Williams, 65, was released Friday after serving two-thirds of his three- year prison term handed down following his May, 1981 conviction on nine counts of bribery and conspiracy charges in connection with the Abscam case.

The 65-year-old former Senate Labor and Human Resources Committee chairman slipped out the back door of a Newark halfway house about 1 a.m., said Katherine Morse, spokeswoman for the federal Bureau of Prisons in Washington, D.C.

Neither Williams nor his wife, Jeannette, could be reached at their home in affluent Bedminster.

A telephone answering machine came on when the number was dialed, and several messages left on the device by The Associated Press were not returned. No one answered the door at the Williams' home either.

A friend of the couple, who came to their two-story, white-with-blue-trim house about 11:20 a.m. to check on it, said Williams would not be home Friday.

Francis Caminiti, a Seton Hall University philosophy professor who lives about three miles from Williams in nearby Gladstone, said, ''He just wants to be left alone.

''He's happy to be out,'' said Caminiti. ''He's quite well, healthy, together.''

Williams became the first senator to be jailed in 80 years when he was sentenced. He served nearly two years of his term at the Federal Prison Camp in Allenwood, Pa., before being transferred to Newark on Nov. 4, 1985.

A liberal Democrat, Williams was considered New Jersey's ''senator for life'' during most of his 24 years in the upper chamber because of his popularity among voters.

He resigned from the Senate on March 11, 1982, facing almost certain expulsion.

Williams was indicted on charges of promising to give an undercover FBI agent posing as an Arab sheik a $100 million loan in return for a pledge of government contracts for a Virginia titanium mine in which he allegedly had an interest.

Six congressmen and 13 other people also were convicted in the Abscam operation.