TORONTO -- Premier Kathleen Wynne can't guarantee that a new deal with correctional workers won't end up costing the province more money, despite repeated pledges to keep such contracts "net zero."

As the province works to eliminate a $7.5-billion deficit, the government has said new public-sector contracts would be cost neutral, meaning any salary increases are offset by savings elsewhere.

But a deal reached this weekend with 6,000 jail guards and probation officers, averting a strike just hours before they were set to walk out, does not settle wages. Outstanding monetary issues will go to arbitration.

Wynne said Monday that the terms already agreed to are "well within" net zero, but she conceded she can't say for sure that the entire deal will be net zero once the arbitrator rules.

"I can't guarantee that, no," she said. "The arbitrator will know the net zero deals that have been reached across government, so the arbitrator will be working within those parameters."

The Ontario Public Service Employees Union said it will certainly seek higher wages at arbitration. An earlier tentative agreement that was rejected by the membership would have given them no increase in the first year, a lump sum in the second year and a 1.4-per-cent raise in the third year of the deal.

The correctional staff are hoping to be paid commensurate with police officers and firefighters, said OPSEU president Smokey Thomas.

"We'll work real hard to get as much as we can."

The monetary issues will be sorted out through expedited mediation-arbitration, a voluntary form of interest arbitration. The correctional workers will also lose the right to strike and disputes in future negotiations will go to binding interest arbitration, like police and firefighters.

The government has said that the deal recognizes that correctional employees' work is "essential," though they are not declared an essential service under legislation in the same way as police and firefighters. But the end result of interest arbitration and no right to strike is the same, said union representatives.

Interest arbitration is often cited by municipalities as a reason for increasing police and firefighter salaries. The Association of Municipalities of Ontario argues that arbitrators place greater priority on replicating similar agreements than on the employer's ability to pay. Private member's bills have made unsuccessful attempts at changing the system.

OPSEU said Ontario correctional workers earn $67,000 a year on average. Federal correctional officers top out around $75,000 a year. The top rates of police and firefighter salaries can hit $90,000.

The union said this correctional agreement will see improvements in time off, improvements in the ability to earn and take time off, as well as a commitment to hire 25 new probation and parole officers.