Tensions between the city and teachers over their t0-the-wire teacher evaluation talks bubbled over in 140 characters early this morning, sending both sides into their respective corners for most of the day.

But state education officials said the city Department of Education and the UFT had been laying the groundwork for a successful submission before the end of the day on Thursday, the deadline for districts to adopt new evaluations or lose state funding.

After a negotiations-packed weekend in which both city and union officials acknowledged that progress had been made, talks went late into the night on Monday at the union’s headquarters. But a little after 1:30 a.m., Leo Casey, a former vice president for the union who has stayed on to finish the evaluations deal, suggested in a Twitter message that negotiations had fizzled out.

“At UFT. Negotiating team prepared to do round the clock negotiating, with full team present,” Casey wrote. “But DOE leaves.”

Department officials were back in the room again today, despite frustration over a union request filed on Monday for a third-party mediator to assist the negotiations through the last remaining issues on the table. (City and union officials both declined to specify what is still up for discussion, but sticking points in the past have been the city’s implementation plan and whether principals would be required to discuss teachers’ ratings with them in person.)

The city’s lawyers rejected the union’s request today and in a statement, Chancellor Dennis Walcott said seeking an independent mediator was the union’s latest effort to negotiate terms unrelated to an evaluation.

”The UFT’s call for a mediator is designed to insert issues into the deal outside of the evaluation’s scope,” he said in a statement. “Mr. Mulgrew should allow his team to negotiate directly the few remaining issues necessary to reach a teacher evaluation deal.”

In his own statement Mulgrew put the chances of a deal in doubt.

“The city’s blind rejection of outside help in resolving these remaining issues is unexplainable, and poses a serious threat to our ability to reach an agreement before Thursday’s deadline,” he said.

But union leaders continued to prepare its members to review a plan should one be agreed upon before the deadline.

Vice President Leroy Barr called members of the union’s evaluations committee to a meeting on Wednesday afternoon. ”Please note that we need you in attendance on Wednesday, January 16th at 4:15PM,” Barr wrote in an email to the 150-teacher committee this evening. ”As promised, we want to give you updates at that time.”

In an interview, Mulgrew said the evaluation committee meeting should not be taken as a sign that a deal is near.

”I told them I’d keep then updated about roughly where we’re at,” Mulgrew said. “What I’ll have to tell them I guess is we’re at a stalemate.”

If the union’s leadership agrees on a plan, a larger group of union members known as the Delegate Assembly must approve it. The Delegate Assembly is scheduled to meet Thursday afternoon, just hours before the state deadline.

Education Commissioner John King said again this afternoon that state officials are prepared to work overtime to review and, if possible, provide feedback for a resubmission before the deadline.

And Regents Chancellor Merryl Tisch, confirming for the first time that state education officials were informally approving elements of an evaluation system before it is finalized, said she remained confident that the city and union would submit an approvable plan.

“We have been led to believe that what they are starting to submit piecemeal is actionable in a positive way from the state education department,” Tisch said. “I would really be surprised at the end of the day, with all the technical assistance that has been available to the districts, with their ability to go online and see all the approved plans, with their ability to backchannel with key people who have been involved with masterminding this entire process, that they would not meet the requirements statutorily.”