UPDATED 09/15/12 10 p.m.

CHICAGO (CBS) –Chicago Teachers Union delegates are expected to meet Sunday afternoon and could decide then whether to end a strike that kept students out of classes last week.

The House of Delegates will meet at 3 p.m. at a Grove Street union hall to discuss contract language that fills out a “framework” the CTU and Chicago Public Schools representatives worked out late last week. The CTU previously said the 800 delegates could vote to end the strike, but on Saturday the union said delegates may decide to take 24 hours to talk with members — a move that would push the walkout into Monday.

“We are a democratic body and therefore we want to ensure all of our members have had the chance to weigh-in on what we were able to win,” CTU President Karen Lewis said in a written statement.

Earlier Saturday, Lewis and CTU members were joined by union members from around the region in a rally that drew an estimated 3,000 to Union Park. Participants later marched west down Washington Boulevard to Garfield Park, led by a high school marching band.

Talks between CTU and CPS representatives went on all day and late into the night at a Michigan Avenue law firm.

The negotiators were working on the fine print. On Friday, they were working on the framework, but a lot of details still had to be worked out. Lewis said she was very comfortable with the framework.

Teacher evaluations, teacher recall in the event of layoffs, and pay increases have been the main focus, although there are a lot of pieces to the puzzle.

LISTEN: WBBM Newsradio’s Mike Krauser reports

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A majority of delegates must approve an end to the strike, and the entire union membership would need to ratify the labor contract.

CTU Vice President Jesse Sharkey says there is a need to keep things private ahead of the important vote.

“The way this discussion comes out in public is with half-characterizations about one part and not the other part; a kind of dynamic where people actually can’t look at the entire thing and consider the settlement as a whole,” he said. “That actually undercuts that process.”

Chicago school officials remained optimistic about the prospect of reaching an agreement.

“We are feeling pretty good,” School Board President David Vitale said on Friday afternoon as talks ended for the day. “We are going to have our kids in school on Monday.”

Saying that the “heavy lifting has been done,” Vitale said both sides have a framework for an agreement.

The CTU delegates’ vote on the contract is expected to come later. Any contract would need to be ratified by the full union membership.