(CNN) The Los Angeles teachers' union rejected the school district's latest offer on Friday, meaning the union is ready to go on strike Monday morning, union leaders said at a news conference.

"At the end of today's session, we declared impasse," said Arlene Inouye, co-chair of the United Teachers Los Angeles (UTLA) bargaining team.

Inouye said the school district's proposal was inadequate and that the district has made insufficient movement in their 21 months of bargaining.

Section 1.5 of the class-size article in the UTLA/LAUSD contract allows the district to unilaterally ignore those caps and averages if it chooses. Every year the district has done so, rendering caps and averages meaningless, and leading to outrageous class sizes. #StrikeReady pic.twitter.com/BzoIomV9QB — United Teachers Los Angeles (@UTLAnow) January 12, 2019

The Los Angeles Unified School District issued this statement Friday night:

"We are extremely disappointed that United Teachers Los Angeles (UTLA) has rejected Los Angeles Unified's revised offer without proposing any counter offer. UTLA has refused to continue contract negotiations. More than 48 hours remain until Monday when UTLA plans to strike, and we implore UTLA to reconsider."

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