The world’s largest auto manufacturer has halted contributions to pension benefits for its most recent U.S. salaried employees, saying it wants to broaden its use of defined contribution plans.

General Motors Corp., Detroit, says it is moving salaried employees hired on or after Jan. 1, 2001 entirely to a defined contribution plan for future service. Salaried employees hired before that date will remain in the defined benefit plan, GM says. However, they will receive a reduced retirement benefit for future accruals under a new career-average pay formula. Pension benefits earned before the transition date will be preserved.

The changes do not affect the benefits of GM’s current U.S. salaried retirees or the vested benefits of former employees, according to GM.

“These decisions are difficult but necessary to position GM for future success and preserve employees’ earned retirement benefits,” said GM chairman and chief executive officer Rick Wagoner.

Salaried employees hired on or after Jan. 1, 2001 and who participate in a pension plan will be shifted to a 401(k) program and receive contributions from GM of 4% of annual base salary. Existing balances under the pension plan will continue to earn annual interest credits, the company said.

GM executives in the U.S. who participate in the supplemental executive retirement plan will have their SERP benefits frozen as of Dec. 31, 2006. On Jan. 1, 2007, the SERP will be brought into line with the revised salaried employee pension plan.

The changes are in addition to moves GM announced last month to cut costs, including capping retiree health-care benefits for U.S. salaried retirees and slashing compensation for GM’s top officers and board members by up to 50%.