Ford announced Friday evening it has halted work on a $3.5 billion battery gigafactory project in southern Michigan it had planned to build with the help of China’s CATL, Kallanish reports.

“We are pausing work and limiting spending on construction on the Marshall project until we are confident about our ability to competitively operate the plant,” a spokesperson said, noting the company is currently considering a number of factors. “We haven’t made any final decision about the planned investment there,” he adds.

The announcement comes at a time of heightened tensions among the US Big Three carmakers and UAW workers striking since 15 September. The UAW wants carmakers to pay workers at battery plants the same higher wages that workers at assembly and engine plants receive.

Reacting to the news, UAW president Shawn Fain said: “This is a shameful, barely-veiled threat by Ford to cut jobs. Closing 65 plants over the last 20 years wasn’t enough for the Big Three, now they want to threaten us with closing plants that aren’t even open yet.”

The union leader added that workers are “simply asking for a just transition to electric vehicles and Ford is instead doubling down on their race to the bottom.”

Ford has not disclosed the considerations it is taking on the investment it first announced in February. The project has faced strong criticism from Republicans in Congress over its dependence on Chinese technology. A probe was started to investigate whether the plant could facilitate the flow of US tax subsidies to China.

The gigafactory is planned to build lithium iron phosphate (LFP) batteries for Ford models, using “knowledge and services provided by CATL.” Specific details of the agreement with the Chinese giant were never disclosed.

Michigan governor Gretchen Whitmer, who remains supportive of the project, said: “Ford has been clear that this is a pause, and we will continue to push for successful negotiations between the Big 3 and UAW so that Michiganders can get back to work doing what they do best.”

Negotiations between the UAW and Ford had been more productive than with Stellantis and General Motors.

President Joe Biden is set to join UAW workers in Michigan on Tuesday.