The U.S. Postal Service is trying to "pit worker against worker" by offering cash bonuses but no hourly wage increases, the president of the largest postal union contends.

"It's just a massage piece designed to divide us," Moe Biller, president of the American Postal Workers Union, said Tuesday as thousands of unionized postal employees held a rally at a Washington hotel.The U.S. Postal Service and its four largest unions, which together represent 660,000 workers, are in the midst of negotiations to replace contracts that expire Nov. 20.

Biller called management's latest offer, which has not been publicly outlined by the U.S. Postal Service, "a piece of garbage designed to pit worker against worker."

Postal Service spokesman Michael West said: "We have negotiated at the table and not in the press. . . . At least for now, we prefer to leave the specifics on the table."

Biller said management had offered the 234,000-member National Association of Letter Carriers a separate pay-incentive plan aimed at dividing the two unions, which bargain together although for separate contracts. Biller's union represents 334,000 postal clerks, maintenance employees, drivers and special delivery messengers.

Assistant Postmaster General David Charters said the pay-incentive plan was part of the Postal Service's goal of holding the rate of postage increases below the rate of inflation.

"We think incentives to support (that) plan are in order," Charters said.

Because the agency, no longer subsidized by taxpayers, must break even over time, its board of governors has proposed raising the cost of mailing a letter from 25 cents to 30 cents next spring.

The unions have not made a counter offer. Biller declined to say how big of pay increases the unions were proposing.