General Motors employees represented by the United Automobile Workers (UAW) union went on strike following the expiration of their 2015 collective bargaining agreement.

Operations at 33 GM manufacturing plants and 22 parts distribution warehouses have halted as 48,000 workers went on strike today, according to the UAW.

The two parties are still in disagreement about wages, health care, profit sharing, job security and seniority for temporary employees, the UAW said in a statement late yesterday.

"We presented a strong offer that improves wages, benefits and grows US jobs in substantive ways and it is disappointing that the UAW leadership has chosen to strike," GM said.

In its latest contract offer, the company alluded to offering "solutions" for its Lordstown, Ohio, and Hamtramck, Michigan, plants, which were idled March. GM did not offer specific details on what the solutions would be.

GM is the largest of the "big three" US automakers and a major consumer of steel and aluminum.

An extended strike could further exacerbate concerns over slowing demand for metal from the auto sector.

Although the latest US vehicle sales and assemblies figures are at or above 2018 levels, broader economic data show signs of low demand, with the Institute of Supply Management's Purchasing Manager's Index indicating the contraction of the manufacturing sector in August for the first time since 2016.

US leading steelmaker Nucor today noted lower auto demand leading to expectations for a drop in third quarter profits.

Conversely, a lengthy shutdown would also reduce steel and aluminum scrap generation at GM's facilities, potentially tightening supply in a market that has been under steady pressure in 2019 because of high supply.