FILE PHOTO: A "UAW On Strike" sign is seen during a rally outside the shuttered General Motors Lordstown Assembly plant during the United Auto Workers national strike in Lordstown, Ohio, U.S. September 20, 2019. REUTERS/Rebecca Cook/File Photo

WASHINGTON (Reuters) - General Motors Co GM.N late on Thursday urged the United Auto Workers union to agree to around-the-clock bargaining to try to resolve a 25-day U.S. strike that has cost the company more than $1 billion in profits, according to a letter seen by Reuters.

The largest U.S. automaker expressed frustration after presenting the union with a comprehensive new contract offer on Monday without getting a formal counteroffer.

The UAW said in a letter earlier on Thursday that work to resolve issues by five committees must be completed first before it will make a comprehensive counterproposal.

“We should engage in bargaining over all issues around-the-clock to get an agreement,” wrote GM Vice President Scott Sandefur in the Thursday letter to the UAW.