United Auto Workers President Gary Jones and General Motors CEO and Chairman Mary Barra shake hands during an event on Sept. 3 to officially open contract negotiations in Detroit.

DETROIT — General Motors CEO and Chairman Mary Barra on Tuesday pleaded for United Auto Workers union leaders to assist, not hinder, the company's ongoing restructuring efforts to better position GM for the future.

Barra, speaking during a ceremony to officially begin negotiations with the union, said the company and union need to be "agile, decisive and disciplined" together more than ever amid a "rapidly" changing auto industry.

"Today, we are at a turning point when it comes to the transformation of the industry and this company," she said during the event inside GM's global headquarters in Detroit. "Our collective future is at stake. We cannot move forward without one another."

UAW leaders took a different position, pledging to use contract negotiations this year with GM to fight the company's plans to potentially close four U.S. plants.

"Speaking on behalf of my brothers and sisters, know this, we will not leave no stone unturned," UAW President Gary Jones said during the event. "We will fight to keep these union plants open and allocate more products here on American soil. It can be done."

His comments came as about 80 laid-off workers and supporters from Lordstown Assembly, a plant in Ohio that GM idled in March, picketed outside GM's headquarters.

Barra did not directly address Lordstown or the other impacted plants in Michigan and Maryland during her remarks. She instead cited a need to be "proactive on all fronts because we are not here merely to survive, we are here to lead it and we are here to win."