WASHINGTON, August 25, 2009 (AFP) - The ailing US Postal Service said Tuesday it was offering buyouts to 30,000 employees to slash $500 million in labor costs as it battles slumping mail volumes and heavy losses.

The USPS, an independent agency of the federal government, said it had negotiated an agreement with two of its employee unions to offer certain employees a financial incentive to retire or resign before the end of the fiscal year on September 30.

The buyout offer targets about 4.5 percent of the agency's workforce, which numbers 656,000 according to its website.

USPS said that advances in mail processing technology and the continuing US recession had led it "to more aggressively match work hours with work load."

The majority of employees eligible for the buyout work in mail processing facilities, it said.

The voluntary layoffs are the latest cost-cutting step taken this year, expected to total more than six billion dollars, the agency said.

The USPS announced on August 5 a net loss of $2.4 billion in its third quarter ending June 30.

The agency has wracked up net losses in 11 of the past 12 fiscal quarters.

The fiscal 2009 net loss at the end of the third quarter was $4.7 billion, compared with a loss in the same period last year of 1.1 billion.

The organization says it may have a September 30 cash shortfall of up to $700 million.