United Auto Workers members on strike picket outside General Motors’ Detroit-Hamtramck Assembly plant on Sept. 25, 2019 in Detroit.Michael Wayland / CNBCDETROIT – The United Auto Workers has summoned local union leaders to Detroit on Thursday for an update on its negotiations with General Motors.The union has traditionally done this when a tentative agreement has been reached or, as was the case a month ago, to discuss and vote on other actions such as a strike.A letter to local union leaders Monday night said the agenda for the meeting included a “contract update and any other agenda items to be determined,” leaving the door open for talks to continue to potentially reach a tentative agreement ahead of the meeting.UAW spokesman Brian Rothenberg declined to comment on the letter. GM spokesman David Barnas confirmed talks are “ongoing,” but declined to comment on details of the discussions. Negotiations between the two sides ended Monday evening and are expected to resume Tuesday morning.If a tentative agreement is not reached by the meeting at 10:30 a.m. Thursday, the union could update local leaders about the discussions in an attempt to determine what to do next.Options for the union moving forward could include:remaining on strike and continuing negotiations with GM; discussing and voting on terms for remaining outstanding issues; moving discussions to another automaker if negotiations have stalled, among others.The summons of local UAW presidents and chairpersons comes following the two sides countering back and forth with proposals. The union on Friday said it had countered an offer from GM.About 48,000 UAW members have been picketing outside GM’s U.S. facilities since Sept. 16. The strike entered its fifth week on Monday.The work stoppage has rippled throughout the automaker’s North American operations, causing thousands of additional layoffs. Wall Street analysts estimate GM has lost more than $1 billion due to the strike.It has also contributed to substantial declines in GM shares during the past month. The stock is down about 9% since Sept.13, the last trading day before the strike. GM shares closed Monday at $35.50, down 0.2%.