General Motors is further cutting benefits for retired white collar workers and their dependents, a letter sent to retirees said.

GM will no longer provide vision, dental and extended-care coverage to retired workers and only medical and prescription-drug coverage will continue, Dow Jones reported, citing the letter.

Life insurance will also be reduced, with bnefits for current retirees 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 CEO Fritz Henderson said in the message to white-collar retirees.

GM's roughly 116,000 salaried retirees have faced increases in co-pays, deductibles and life insurance and the automaker recently eliminated medical coverage for retirees eligible for the US Medicare scheme. The most recent cuts affect retirees not covered by Medicare, Dow Jones said.

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

The bankruptcy court judge overseeing GM's case will hold a hearing in New York on 25 June 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 would 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 would pay half the $20bn owed to the retiree trust, plus give the trust an equity stake in the new company.