General Motors Corp. (GMGMQ) is further slashing benefits to retired white-collar workers and their dependents, according to a letter sent to retirees.

GM will no longer provide vision, dental and extended-care coverage to retired workers. Only medical and prescription-drug coverage will continue.

Life insurance also will be reduced. Benefits for current retirees will be capped at $10,000, while future retirees will receive life insurance worth half their annual base salary. The reductions are down from 75% of workers' annual salary.

"These are very difficult changes to make, but unfortunately necessary to position the New GM to win - and win now," GM Chief Executive Fritz Henderson said in a message to white-collar retirees.

The cuts come in addition to deep reductions made in recent years as GM has undergone a wrenching restructuring in recent years. GM has around 116,000 salaried retirees.

Salaried retirees have faced increases in co-pays, deductibles and life insurance. Recently, the auto maker eliminated medical coverage for retirees eligible for Medicare. The most recent cuts affect retirees not covered by Medicare.

GM has said it intends to continue funding pension plans for all retired workers.

GM's move to cut benefits faces opposition in bankruptcy court from a retiree group challenging the cuts and seeking separate representation.

The bankruptcy court judge overseeing GM's case will hold a hearing in New York on June 25 to consider granting the retiree association's request to appoint a committee so they can negotiate with the company and protect their interests.

Under GM's proposed overhaul, retirees represented by the United Auto Workers union will continue to have their health benefits funded, but could see substantial cuts. As part of GM's new deal with the UAW, the auto maker will pay half the $20 billion owed to the retiree trust, plus give the trust an equity stake in the new company.

-By Sharon Terlep; Dow Jones Newswires, 248-204-5532; sharon.terlep@dowjones.com.