U.S. auto parts suppliers are shifting their loyalties and resources to Japanese auto makers at the expense of the Big Three, which generally treat suppliers as adversaries, according to a new study.

U.S. auto makers, relying more than ever on profit-eroding consumer incentives, repeatedly seek price reductions and multimillion-dollar cash givebacks from parts and components makers.

Suppliers, in turn, are responding by giving them less support in areas such as service and research and development, said the study by the Birmingham-based firm Planning Perspectives Inc.

"In all the other industries we've studied such as aerospace, electronics and computers, no one treats their suppliers as poorly as the U.S. auto makers," said Planning Perspectives' John W. Henke Jr., who has studied supplier/auto maker relations since 1990 and began this particular survey in 2001.