Discussions between the UAW and Fiat Chrysler aimed at restructuring a tentative agreement overwhelmingly rejected by workers have reached a critical juncture with the union issuing a strike notice.

The strike notice came as two people familiar with the talks told the Free Press that negotiations had, at least for some time, broken down with UAW negotiators leaving the bargaining table.

UAW Vice President Norwood Jewell sent a letter today to the company’s top negotiator Glenn Shagana, vice president of employee relations at FCA, giving formal notification that the union is terminating the current agreement that had been extended while negotiations continued. The letter, obtained by the Detroit Free Press, said all agreements are terminated as of Wednesday at 11:59 p.m.

Fiat Chrysler confirmed that it received the notice but said discussions between the two parties are ongoing.

Even so, the strike notification alone raises a host of new questions and escalates the urgency for both sides to reach an agreement on a new contract.

“FCA US confirms that it has received strike notification from the UAW,” the Auburn Hills automaker said in a statement Tuesday. “The company continues to work with the UAW in a constructive manner to reach a new agreement,” the statement continues, suggesting talks may be continuing at some level.

The UAW’s notice appears to be a serious threat, according to a UAW official who declined to be named because of the sensitivity of the preparations. The UAW’s elected leaders are being asked to pick up picket signs and have been asked to meet with the automaker’s plant management to make preparations to keep core machines and services operating during a potential strike for safety reasons, the person said.

UAW President Dennis Williams had decided to go back to the Auburn Hills automaker to try to address employee issues after 65% of Fiat Chrysler workers voted against a tentative agreement that union officials and the company hashed out over two months of negotiations.

A spokesman for the UAW declined to comment.

Meanwhile, workers on the UAW’s Facebook page are saying they have been told that notices of strike deadlines are being posted for 11:59 p.m. on Wednesday.

The strike deadline postings are ambiguous, said Kristin Dziczek, director of the Labor & Industry Group at the Center for Automotive Research..“It doesn’t tell the membership where things stand.”

It might be a transitional state until the UAW international executive board authorizes a walkout, she said.

A national walkout or strike would threaten to quickly destabilize Fiat Chrysler, which has been profitable in recent years, but is the weakest company of the Detroit Three. It also could do tremendous damage to the relationship between the union and the company that has markedly improved in recent years compared with prior decades.

“They don’t have to go long if they do strike,” Dziczek said. “A strike causes pain on both sides and applies pressure to get back to the table.”

Striking costs each individual in the pocketbook and is not done lightly, said Dziczek, who predicted from the start that a strike was likely at FCA but takes no delight knowing that she might be proven right.

“It is a financial strain to walk the picket line for $200 a week.”

Nor is it clear whether the union will issue a targeted strike at key plants or a full-scale strike at all plants.

A targeted strike at pinch points like the Kokomo transmission plant would mean a few thousand workers would have to rely on $200 in weekly strike pay while workers at other plants that go down because they can’t build vehicles without transmissions would receive unemployment benefits and not be hurt as much financially by a walkout.

Targeted strikes don’t put as big a dent in the UAW’s strike fund, but Dziczek said the fund is big and that is not a concern.

Nor does she think a strike would be lengthy.

Fiat Chrysler will be most hurt by the idling of the Kokomo transmission plant and the vehicle assembly plants in Toledo and Jefferson North that make popular Jeeps and the Warren Truck plant that makes the Ram full-size pickup.

“That would hit Fiat Chrysler where it hurts.”

Contact Brent Snavely: 313-222-6512 or bsnavely@freepress.com. Follow him on Twitter @BrentSnavely.

Contact Alisa Priddle: 313-222-5394 or apriddle@freepress.com. Follow her on Twitter @AlisaPriddle