One of the more vulnerable suppliers is American Axle & Manufacturing Holdings, which while not financially weak, derives more than 70 percent of its sales from GM, Lombard said.
Some suppliers may not count GM as a large customer, but are in weaker financial shape and cannot afford to lose any business, Lombard added, pointing to Visteon. Others with GM business include Delphi, Goodyear Tire & Rubber, Johnson Controls, Lear and Tenneco.
The first to feel the pain, however, could be smaller, privately held suppliers, who cannot turn to Wall Street for financial aid, Lombard said.
"For every car not built, that's 10,000 parts not used and, eventually, that will impact people," said Neil De Koker, president of industry trade group Original Equipment Suppliers Association.
The United Auto Workers (UAW), which represents more than 73,000 GM factory workers, called the national strike after the union failed to reach a deal that would allow the Detroit automaker to cut its $5 billion annual health-care bill.
GM -- with plants spread throughout the United States, Canada and Mexico -- along with U.S. rivals Ford Motor and Chrysler, is seeking concessions from the UAW to close a labor cost gap with Toyota Motor and other Japanese automakers operating in the United States.
Analysts said the suppliers had a long time to prepare as the talks have been going on for months. Officials with many suppliers echoed that sentiment.
"We're prepared to address our customers' needs, whatever they are," American Axle spokeswoman Renee Rogers said, declining to elaborate.
Others said they will adjust as needed.
"Delphi will make the appropriate adjustments to its customer delivery schedules based on specific site circumstances," company spokesman Lindsey Williams said in an e-mail message.
"With respect to non-GM customers, Delphi will continue to produce and deliver products and services in line with customer schedules and contracts. It is actually too soon to characterize the site-by-site impact at this time."
Lear spokeswoman Andrea Puchalsky said how its plants are affected depends on products and the strike's duration, and could result in temporary layoffs. GM makes up about 30 percent of Lear's business.
"Some locations don't supply GM. Some supply multiple customers and how it impacts us depends on the length of the strike and the facilities as well," she said. "In a case where it's seat production, which is just-in-time, we would shut down immediately."
Officials with Goodyear, Tenneco and Visteon were not immediately available to comment.
In the end, many suppliers see the U.S. automakers' fight as also affecting their future.
A Johnson Controls spokeswoman pointed to comments made by Stephen Roell, who takes over as CEO Oct. 1, in a interview last week with Reuters. He said the U.S. automakers need economic concessions from the UAW to remain competitive, calling it "critical to the survival of those companies."