General Motors Chief Executive Mary Barra has stepped into contract talks with striking auto workers, asking the union to wrap up outstanding issues and respond to a company offer made this week. But in a letter to GM’s top bargainer Thursday, United Auto Workers Vice President Terry Dittes wrote that there won’t be a response to Monday’s offer until committees working issues are finished. He didn’t know how long that will take. Details of the Wednesday meeting between Barra and top union bargainers were disclosed in the letter, which was obtained by The Associated Press. It’s an indication that there won’t be a quick end to the nearly month long strike by 49,000 workers that has halted production at all of GM’s U.S. factories.