For the fourth time, locked out union workers with American Crystal Sugar will vote on a contract proposal to end the 16 month dispute with company management, Minnesota Public Radio reported.

More than 1,300 union workers from plants in Minnesota, North Dakota and Iowa were locked out since Aug. 1, 2011, after rejecting the company's final offer.

MPR said 90 percent of the union's workers rejected the first two contract votes, followed by a rejection by 63 percent of the workers on the third vote.

A labor relations expert at the University of Minnesota's Carlson School of Management told the Star Tribune that he expects a closer vote since seasonal jobs for locked-out workers are harder to get in the winter months -- a crucial time to not have income because of heating bills.

At issue is contract language that allows for the promotion of workers regardless of seniority. Also of concern to the union is language that would allow the hiring of temporary workers.

A union official said last week that the contract workers are voting on Saturday is the same contract that was rejected in June.