By David Shepardson

United Auto Workers President Shawn Fain said Monday the union is prepared to negotiate around the clock with the Detroit Three automakers with just four days before a potential strike of 146,000 U.S. autoworkers.

"We are ready to negotiate in Detroit 24/7, just as we have been for the past seven weeks since we gave them our Members Demands," Fain said in a statement. "Despite receiving no response for over a month, when the CEOs are ready to make a serious offer we'll be there, day or night."

Chrysler-parent Stellantis said earlier Monday it planned to make a new counteroffer to the UAW after the union made its own revised offer on Sunday. The current four-year labor deal expires on Sept. 14 at 11:59 p.m. ET.

The UAW on Friday had rejected revised offers from Stellantis, General Motors and Ford Motor. GM made a new offer to the UAW over the weekend, but the details were not immediately available. GM declined to comment.

UAW bargainers met with GM and Ford on Sunday and made progress, officials told Reuters.

"We are on a good path and remain committed to reaching a tentative agreement without a work stoppage that would negatively impact our employees and our customers," Stellantis told employees in a an email Monday, adding that Stellantis and UAW subcommittees reached tentative agreements in a number of areas, including health and safety.

Stellantis said Friday it had offered U.S. hourly workers a 14.5% wage hike over four years, much less than the 46% wage hike the union initially sought.

GM said Thursday it offered workers a 10% wage hike and two additional 3% annual lump-sum payments over four years. Stellantis last week did not offer additional lump-sum payments.

Ford last week hiked its offer to a 10% wage hike and lump sum payments after offering a 9% wage increase through 2027 and 6% lump sum payments.

The Detroit Three have offered to minimum pay for temporary workers to $20 an hour and reduce the time necessary to reach top wages for permanent autoworkers from eight years to six years.

The union's demands include a 20% immediate wage increase followed by four 5% annual wage hikes, defined-benefit pensions for all workers, 32-hour work weeks and additional cost-of-living hikes.

Stellantis previously offered $10,500 in inflation protection payments over the four years, while GM is offering $11,000 and Ford $12,000.

(Reporting by David Shepardson; Editing by Nick Zieminski)