LANSING, Mich. (AP) — Many manufacturers support a new trade deal with South Korea, one reason President Barack Obama and his South Korean counterpart will visit a plant Friday where General Motors is building cars with South Korean parts.But the pact also will make it easier for South Korea to undercut some U.S. companies, leaving many workers leery of the deal.The agreement Congress passed Wednesday has support from workers in the automobile and food packing industries, who say it will create American jobs by increasing auto and beef exports to South Korea.Textile and steel workers say it will mean more jobs shipped offshore. Steelworkers say auto parts makers will lose business even if automakers export more vehicles.It's the biggest U.S. free-trade deal since the 1994 North American Free Trade Agreement.