Post Age, the authorative newsletter covering mail matters, says the U.S. Postal Service is preparing a proposal for the Postal Rate Commission that will mean higher prices and less service. Editor Art Brandel says USPS will ask for authority to raise the 13-cent, first-class stamp rate to 16 cents, and drop Saturday delivery.

An outside study commission, appointed by the President and Congress, has recommended the USPS cut to 5-day delivery to save money and avoid even larger future price increases. But that was a proposal for the Congress and the White House, not a mandate to the USPS to do it.

Chairman Robert N. C. Nix (D-Pa.) has warned the USPS not to jump the gun with either a price raise or service cut until his Post Office-Civil Service Committee and other congressional watchdog units take a look at the alternatives. Postal unions oppose the 5-day plan because it could cost between 20,000 and 30,000 jobs.

Backers of the 5-day delivery plan argue that it will help hold down future stamp price increases. Also, they say that increased labor costs (for 6-day delivery) could force the USPS deeper in the red, and require it to lay off many more workers than would be affected by an orderly reduction of service.