General Motors Co. may burn through $1 billion in cash if the United Auto Workers union’s strike lasts a week, S&P Global Ratings said.

Most of the cash GM goes through can be recovered when production resumes, the credit rater said in a statement Wednesday. S&P estimates the strike could result in lossed production of as many as 45,000 vehicles if it lasts a week.

The strike that the UAW called on Sunday limits the potential upside for GM’s credit rating in the near term, and “could introduce additional downside risks if the strike were to prolong beyond two weeks,” S&P said. GM is rated BBB by the firm, the second-lowest investment-grade level.