"It's clear that there is no real intent to get to an agreement," Barra said in an emailed night. "It is clear Shawn Fain wants to make history for himself, but it can't be to the detriment of our represented team members and the industry."

Fain has consistently said the union is available to negotiate 24/7 and has in turn accused the automakers of slow-walking negotiations.

GM's newly announced line of credit will require the automaker to maintain at least $4 billion in global liquidity and $2 billion in U.S. liquidity. The terms of the credit agreement also restrict GM from mergers or sales of assets and limits on other, new debt. As of June 30, GM's total automotive liquidity was $38.9 billion.

The credit line comes more than a month after Ford to help it manage through "uncertainties" in the market.