The expected resignation today of Arlington County Sheriff James A. Gondles Jr. comes at an awkward time when Arlington is building a new county jail, lobbying for a regional jail and mired in controversy over a proposed jail release center -- all projects for which he has been an important cheerleader.

Gondles (D) will resign to become executive director of the American Correctional Association, according to sources in the group. Gondles, who has been sheriff for 12 years, would not comment yesterday on his plans, but said he would make an announcement today.

Once Gondles has resigned, the county Circuit Court will appoint an interim sheriff. The next election for sheriff is scheduled for November 1991, but if Gondles's resignation is effective before July 10, a special election would be held on Nov. 6 of this year.

Gondles's opponent in a hotly contested 1987 election, Ronald Hager, said yesterday he is "very interested" in running again.

Gondles's early departure from office comes at a crucial time for the county corrections system. Construction of the $42 million county jail has not yet begun. Gondles led the successful campaign to get voters to approve a $35 million bond issue to pay for it.

The director of corrections at the current county jail, David Bogard, said Gondles's departure should not affect the plans for the jail if the court appoints someone from within the department as acting sheriff.

"Whoever is chosen by the Circuit Court will not want to redesign the jail, which at this point would cost tens of thousands of dollars," Bogard said.

Gondles also was active on a committee lobbying for the construction of a minimum-security regional jail.

The sheriff of Alexandria, James H. Dunning, said Gondles's resignation should not hamper progress on the regional jail, assuming that the county continues to support the idea.

Gondles also has been one of the leading supporters of a plan for the jail release center on Four Mile Run Drive near Barcroft Park. More than 400 people turned out at a Planning Commission meeting this week, many of them angrily denouncing the proposal.

The corrections association, with 24,000 members, promotes work, housing and safety standards for jails, prisons and other correctional institutions.

Gondles will head a staff of 95 and will be paid "more than he makes now, but under $100,000," the source said. Gondles was paid $77,000 as sheriff last year.