Bargainers for General Motors and the UAW met until early evening Saturday in an attempt to reach a tentative contract agreement that the union's 46,000 members would ratify.

It was the 13th day of the UAW's nationwide strike against GM and followed sessions that went past midnight Thursday and into Friday evening.

As these negotiations continue, the UAW is also working separately to resolve a strike by 850 janitors employed by Aramark who work in five GM facilities. Those janitors went on strike one day before union members at GM did. A source close to the talks said it appears the UAW is trying to reach tentative agreements with Aramark and GM simultaneously so that workers from either side will not have to cross the other's picket lines.

Meanwhile, Friday morning, some UAW regional directors met with leaders of UAW locals to brief them on the talks.

“They folded some issues in at the subcommittee level and handed them to the main table because they were not getting further in their bargaining at that level," said a local union leader, who attended a three-hour meeting with regional directors Friday, but asked to not be identified. "In short, we’re not getting any closer than we were two days ago.”

It is always possible for a breakthrough to suddenly speed talks toward a tentative agreement.

But sources close to negotiations characterized each side as dug into their positions. For example, GM is said to want hourly workers to pay more for health care, but even more important to GM, to lower its labor costs, it wants a higher percentage of temporary workers at each plant. The union is holding to a firm "no" on both requests, sources said.

Even after a tentative deal is struck, the strike could last at least a week longer. The UAW is considering keeping members on the picket lines until the GM rank and file ratifies the deal, as the Free Press has reported.

More:GM, UAW aren't close — agreement might take another week of talks

More:GM strike may stretch out awaiting UAW workers' vote on tentative deal

At the table

In a letter to members, the UAW said Wednesday that "all unsettled proposals are now at the main table and have been presented to General Motors and we are awaiting their response. This back and forth will continue until negotiations are complete."

The fact that the subcommittees elevated the difficult issues to the main table could be read two possible ways, said Marick Masters, director of labor at Wayne State University.

"They put them on the front table in the hope that the people at the top will reach a solution," said Masters. "Or, that they could not reach agreement at the committee level and they’re kicking the problem upstairs."

Masters said the overriding difficulty the UAW negotiators face is getting a tentative agreement membership will accept without much of a sales pitch. Therefore, "they are very reluctant to make a trade-off."

At the same time, said Masters, "I don’t think that GM will concede on the issue of wanting a more flexible workforce," a reference to GM's desire to add more temporary workers.

Sources familiar with the negotiations told the Free Press the unsettled proposals now at the main table are economic issues. These are the main ones:

UAW workers' share of health care costs

Temporary workers

Wage increases

Building more product in the United States.

Strike costs

Union members went on strike at 12:01 a.m. Sept. 16 after its 2015 contract expired at midnight Sept. 14.

Two hours before it expired, GM made what it considered a tantalizing offer that included among other things:

A wage increase

Added health care benefits

Solutions for two of its idled assembly plants

Electric pickup production

Battery cell manufacturer

$7 billion in U.S. investments and 5,400 jobs.

The Free Press has learned that only half of those jobs would be new hourly jobs, the rest would be considered retained because of the new investments. Likewise, part of the $7 billion would come from joint ventures and develop entities that would have a separate contract with the UAW. Those workers likely would be paid less than Detroit Three workers.

Absent from GM's offer was any mention of the fate of temporary workers, a big issue. The union wants to create a process for them to become permanent and earn better pay and benefits along the way.

Likewise, GM's initial offer on Sept. 14 to the UAW called for members to pay 15% of their health care costs. They currently pay a total of about 3%, far less than the average U.S. worker's 28%. The UAW balked at GM's offer and the company walked it back to 3%.

But the topic is back up for discussion, said one of the people familiar with the talks who characterized issues for the Free Press. GM is again suggesting that UAW members pick up a greater portion of the cost for health care, but it is unclear how much. GM said it pays about $900 million a year for U.S. hourly employees' health care.

Labor matters

Wages remain a sticking point. In its initial offer, GM proposed a wage increase of 2% in two years of the four-year deal and lump sum payments of 2% in the other years. The UAW rejected it. That falls short of GM's 2015 contract when workers got a 3% wage hike two years and 4% lump sum the other two years. Sources familiar with the talks said the parties remain "far apart" on that issue.

The UAW also wants to narrow the pay gap between different tiers of workers. GM hourly workers hired before 2007 are known as the legacy workers. They make about $31 an hour. They also retire with a lifelong pension. But those hired after 2007, which is nearly a third of GM's hourly work force, start at $17 an hour. They are called "in-progression" because they can work up to $28 an hour over eight years. They get a 401(k) retirement account instead of a pension.

More:UAW: 'Pay hasn't caught up with inflation' after 'bankruptcy sacrifices'

More:Why GM-UAW talks have taken this long

Suspicion and distrust

While those close to the talks say bargainers are unemotional and focused, publicly, the two sides have appeared at odds. Early Thursday, GM reversed itself on a decision it made early in the strike that angered the union. GM blindsided UAW leaders when it said it was kicking the cost for health care to the union's strike fund to pay for COBRA coverage on striking workers.

GM has now decided to pay health care costs of strikers after all rather than leaving that to the UAW. Even that reversal came as a surprise to UAW leaders after many strikers had filed for COBRA coverage last week.

"GM has blindsided the UAW on several occasions," beyond the health care coverage issue, said Masters.

He noted that GM surprised the UAW when it released a lot of details of its initial proposal to the UAW, an unusual move during negotiations.

"I think GM is using whatever leverage it has to try to create a stage where the UAW feels it has to make a settlement," said Masters. "It may have backfired on them, when they said they wouldn’t pay the health care and now they are saying they would do it. Or they’re just misreading the situation."

The long negotiations, coupled with the public posturing, leads Masters to conclude: "I’m not certain how well the parties are communicating with each other. I’m not certain how well the parties are listening to each other. I question how well they communicated even before they started negotiating. This may be a case where the distrust between the parties and the suspicion between the parties is such that they have a difficult time communicating.”

Contact Jamie L. LaReau: 313-222-2149 or jlareau@freepress.com. Follow her on Twitter @jlareauan. Read more on General Motors and sign up for our autos newsletter.