Commercial shipping operations at the Port of Montreal could be shut down Monday by a labour dispute.

The Maritime Employers Association issued a news release saying it will lock out 850 members of the Longshoremen's Union, CUPE, Local 375 , at 8.a.m. ET on Monday, until further notice.

The association said its hand is being forced by the union's refusal to acknowledge the urgency of the matter and the need to make radical changes to the current collective agreement.

The Association said the lockout is also necessary given that pressure tactics have begun to impede port operations.

The main issues in the dispute are job and revenue security, and the association said it hopes the lockout will prompt union officials to look more realistically at the challenges the maritime sector is facing.

The association said that in today's market it can no longer accept such a large gap between the amount of hours worked by longshoremen and paid for and the amount of hours not worked but still fully paid for.

Union representatives were not immediately available for comment.