There is still "a long way to go" before tentative labor agreements can be reached between the big three U.S. automakers and the Detroit-based United Auto Workers (UAW) to end the strike which has entered the fourth day, said UAW President Shawn Fain Monday.

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"We've put full offers to all three companies before the strike deadline, and we've really had minimal conversations over the weekend," Fain said.

The union met with Ford Motor Co. and General Motors Co. over the weekend, and with Stellantis on Monday, yielding no results.

Fain said 20-percent not-compounded wage increases offered by the automakers "is not enough," after what the union sacrificed to save the companies during the Great Recession and bankruptcies.

The union had requested 40-percent not-compounded or 46-percent compounded wage increases, and now is asking for a 36-percent wage increase over four years.

The elimination of tiers wage remains one of the key issues, Fain said. The automakers have suggested reducing the timeline to get to the top wage to four years, down from eight, while the UAW wants it to take just 90 days.

The previous contracts between the big three automakers and the union workers expired at midnight on Thursday. A total of 12,900 workers at a Ford plant in Wayne, Michigan, a Stellantis NV plant in Toledo, Ohio and a GM plant in Wentzville, Missouri, immediately went on strike.

The union has threatened that more plants could join the strike based on how talks continue. Nevertheless, Fain refrained from stating how soon that could be.

As a result of the strike, Ford on Friday temporarily laid off the rest of 600 workers at its Michigan Assembly Plant in Wayne.

Ford could face strikes at its plants in Canada if it fails to reach a tentative agreement with Unifor -- a Canadian autoworker union representing roughly 18,000 autoworkers at Ford, General Motors Co. and Stellantis NV in Canada -- ahead of the union's midnight strike deadline on Monday, when current contract expires.

Unifor has selected Ford as the lead company in talks with all three automakers. But up to this point, the two has not reached a tentative agreement.

Unifor has advised more than 5,600 members at Ford facilities in Canada to prepare for all scenarios, including strike action, the Detroit News reported.