By Bryan Woolston

BOWLING GREEN, Ky. (Reuters) - General Motors Co shifted health insurance costs for its striking workers to the United Auto Workers union as its members walked the picket line for the second day on Tuesday.

The UAW on Monday launched the first company-wide strike at GM in 12 years, saying negotiations toward a new national agreement covering about 48,000 hourly workers had hit an impasse.

This year's talks between the union and GM, Ford Motor Co and Fiat Chrysler Automobiles NV (FCA) were expected to be tough, with thorny issues such as healthcare costs, profit-sharing and the use of temporary workers on the table.

The UAW said Tuesday that some progress had been made during talks. As of Tuesday evening, talks were still continuing among some committee-level bargaining groups but no deal was imminent, officials said. The strike has now surpassed the length of the nearly two-day 2007 GM work stoppage.

Workers on picket lines outside GM factories waved signs declaring "UAW On Strike." In Bowling Green, Kentucky, they blocked the three entrances to the assembly plant, which normally builds the Chevrolet Corvette.

Salina Alexander, who works in the Kentucky plant's paint shop, said the strike is about GM sharing some of its profits with union-represented employees who helped bail out the carmaker during its bankruptcy. "We hung in there with them. They can give us something back."

Meanwhile, GM said coverage for the striking workers' health insurance reverted to the union, which unsuccessfully sought to have the No. 1 U.S. automaker cover those costs through the end of the month. That places another drain on the union's strike fund.

"We understand strikes are difficult and disruptive to families," GM spokesman Jim Cain said in an email. "While on strike, some benefits shift to being funded by the union's strike fund, and in this case hourly employees are eligible for union-paid COBRA so their health care benefits can continue."

GM has said in the past that it annually spends about $1 billion a year on healthcare coverage for its hourly workers, suggesting the monthly cost per worker is in the range of $1,700 to $2,000. The UAW on its website said its strike fund covers certain benefits such as medical and prescription drugs, but not dental, vision and hearing. (https://uaw.org/strike-faq/)

A UAW spokesman had no immediate comment, but Terry Dittes, vice president in charge of the union's GM department, in a letter to union leaders on Tuesday, said the UAW would review its legal options regarding GM's decision.