DETROIT - Government aid and timely payments by General Motors, Ford and Chrysler have held off the predicted collapse of the nation's auto-parts supply base, but industry officials say more bankruptcies are coming as the effects of Detroit's temporary factory closures ripple through the economy.

Hundreds of companies across the country make everything from bolts to axles to transmissions, shipping them to Detroit Three factories, and those of foreign automakers with U.S. plants.

Some supply parts to others that make larger components, creating a chain of companies that many thought would snap if payments were interrupted to firms already under stress because of the U.S. auto sales slump.

While there have been about 20 supplier bankruptcies this year, most suppliers have managed to hang on despite Chrysler Group L.L.C. and General Motors Corp. entering bankruptcy protection and shuttering their factories for weeks to keep inventory under control.

"There was not the Armageddon that could have been there," Chip McClure, chairman and chief executive officer of supplier ArvinMeritor Inc., which makes parts for cars and heavy trucks.

Suppliers already were hurting last year, when the U.S. auto market dropped to an annual selling rate of around nine million after peaking at 17 million in mid-decade.

Many thought the whole system would collapse because the automakers would be unable to keep making payments, but government cash infusions and payment guarantees for GM and Chrysler kept most suppliers afloat, said Dave Andrea, vice president of industry analysis and economics for the Original Equipment Suppliers Association.

Before filing for bankruptcy, GM made payments to suppliers early, which also helped cash-strapped companies avoid trouble, Andrea said.

Now, though, many could be in trouble again with GM and Chrysler temporarily shutting some factories for up to three months due to growing inventories. If the factories aren't running, suppliers have no income, and there's a 45-day lag between when they ship parts and when they are paid again.

"It isn't over yet," said Bob McKenna, president of the Motor Equipment Manufacturers Association, another industry trade group.

Large suppliers Visteon Corp., once a unit of Ford Motor Co. and that company's biggest supplier, and Metaldyne Corp. already have filed for Chapter 11. Barclays analyst Brian Johnson said in a note to investors yesterday that Lear Corp., which already has missed interest payments, is vulnerable to a bankruptcy protection filing by June 30.

Supplier trade groups are lobbying for $8 billion to $10 billion more in loan guarantees to suppliers to help them raise money to buy raw materials and pay employees as Chrysler and GM resume production.