Can an employer withhold a week's pay when we're supposed to get paid for two weeks?

My employer sent an email this past weekend to all employees stating that due to "economic reasons" they were going to withhold a week's pay from our next check. We get paid every two weeks, for two weeks of work. Is it legal to just decide to withhold a week's pay and say that the only way will get the money for that week's work is when we leave the company? Or they said we could get an advance along with the pay for one week. If they have the money to offer advances, I would think they have the money to just pay us for that one week instead of being in debt to the company for an advance. This doesn't seem legal to me.