HONOLULU -- Hawaii's biggest public workers union on Monday said Gov. Linda Lingle's plan to furlough state workers is illegal and it plans to block it.

The leader of the Hawaii Government Employees Association said the union will either go to court or the state Labor Relations Board to seek an injunction blocking furloughs, which are scheduled to start in just over two weeks.

The governor ordered the three-day per month unpaid furlough to save $688 million in payroll by 2011. The union said she cannot do that.

"We believe this is a pay cut, and pay cuts by their nature are negotiable matters," HGEA President Randy Perreira said.

The union said it is willing to negotiate pay and benefit reductions, but will not give up as much as the governor wants.

The state labor spokesman, who is a union member, said he prefers furlough to the alternative.

"A mass layoff would be difficult and scary. So, if we have to take these three days you know maybe that's better than a lot of people losing their jobs," Labor Department spokesman Ryan Markham said.

"The great majority of calls that I have received personally are just wanting us to continue the fight because they see this as just wrong," Perreira said.

Adding to the anxiety about pay cuts is the uncertainty about how the furlough will be implemented.

There are a lot of ideas about how a furlough could work being floated around. One comes from California, where workers have a furlough bank. They have their pay withheld, but then they can use their furlough days later as if it were vacation.

"Our concern in the department of labor is to make sure impact on the public is minimized," Markham said.

The union said it has heard lots of rumors about furlough plans, but nothing specific.

"There is no rhyme or reason to what we have heard so far," Perreira said.

When she made her furlough announcement, the governor promised specifics in 10 days, but it has been two weeks. The governor's negotiators have scheduled a meeting with union leaders later this week, but it not clear why.