Negotiations for new public service union contracts begin this week in Ottawa, and the stakes are high for government workers, given the government's commitment to trimming the public service to save money.

Negotiating teams for five bargaining units of the Public Service Alliance of Canada come together in Ottawa today.

The biggest union representing federal workers started developing its demands earlier this year, including competitive pay and an overhaul of the process in which workers are laid off.

From the other side of the table, the Treasury Board has said the government's priority is modernizing the disability and sick leave system. The department said it looks forward to working with bargaining agents to make that happen.

Gilles LeVasseur, who teaches law at the University of Ottawa's Telfer School of Management, said there's a "determined agenda to cut costs on the benefits, on the pension reforms."

But LeVasseur said the union might be able to compromise on other issues.

"Let's get, for example, more mobility for promotions, or grant more opportunities for employees to get their tuition fees paid if they go to school, provide other program incentives that would help employees benefit their long-term career goals," he said. "You may benefit in other areas that have long-term benefits for the employees."

But so far, Public Service Alliance leaders aren't signalling that they'll back down.

Heading to the table, they said they will not accept changes to sick leave provisions.