AUGUSTA — The McKernan administration has expanded its state hiring freeze in an effort to reach the $15 million in payroll savings it promised lawmakers it would achieve as part of this year’s budget-balancing package, Finance Commissioner H. Sawin Millett said Tuesday.

The tougher hiring restrictions are among several steps the administration is taking to augment the $9.3 million in savings produced so far by state employees volunteering to retire early or reduce their work weeks in response to incentives offered by the administration.

“I think we’re going to be fairly close when all is said and done,” said Millett. He said he would not have conclusive figures until his office finishes balancing the books for the fiscal year that ended June 30.

He noted that the administration previously had abandoned hope of achieving the entire $15 million in savings through voluntary reductions.

“I think, in hindsight, you’d have to say (that goal) was overly optimistic,” he acknowledged.

Millett said the administration concluded several weeks ago that actual layoffs would not be necessary, however.

Millett described the modifications in the hiring freeze as “a broadening and a continuation” of the freeze that Gov. John R. McKernan imposed on Sept. 30, which applied to most vacant positions financed by the state’s General Fund. Exemptions were provided for certain types of jobs, such as state troopers and prison guards, as well as newly created positions and vacancies filled through in-house promotions or temporary hirings.

The new policy extends the freeze to new positions and promotions into vacant ones, and it also includes slots covered by all state funds except the Highway Fund, the commissioner said.

Millett, who is McKernan’s top budget adviser, said the administration also will continue to accept applications for voluntary reductions in work hours “for the indefinite future.” Applications received in the past week alone, he said, yielded between $300,000 and $400,000 in savings.

Further, some employees were allowed to take sabbaticals or sporadic days off prior to the scheduled July 1 opening of the programs, which Millett said also should boost the total savings from the voluntary programs by “a few hundred thousand” dollars.

More than 1,500 state employees have signed up for the programs, some of which included financial incentives, out of the 1,691 who initially had expressed interest in March, Millett said.

The payroll savings were a major element in the array of spending cuts, program deferrals and other steps that the Republican governor and the Democrat-dominated Legislature endorsed earlier this year to forestall a potential $210 million deficit through mid-1991.