U.S. Postal Service management is expected to propose an increase in first-class mail rates and possibly an end to Saturday deliveries within the next 30 to 60 days.

At a meeting of the Postal Service board of government corporation projected an operating deficit of $2.4 billion in the year from March 23, 1978, through March 24, 1979.

To overcome that possible loss - which does not count government subsidies that count as revenues - postal officials are expected to ask the Postal Rate Commission for an increase in first-class mail rates from 13 cents an ounce today to 16 cents. Because of the months involved in postal rate hearings, the higher rates would not take effect until 1978.

There is a possibility that Postmaster General Benjamin F. Bailar will recommend an end to Saturday deliveries of mail as one alternative to keep first-class rates lower.

Postal officials use, as a general rule of thumb, a formula that translates each increase of one cent in first-class postage to added revenues of about $1 billion a year - $600 million from first-class and the balance from associated rate increases for other classes of mail.

Thus, to overcome a deficit projected at $2.4 billion, a first-class boost of three cents an ounce would be necessary. However, postal officials said they could save $400 million a year by ending Saturday delivery of mail.

If an end to sixth-day delivery is approved, that means that first-class postage might be kept to 15 cents an ounce. However, an unknown factor is the amount of mail-volume that might be lost with higher rates and a Postal Service spokesman cautioned yesterday that a 16-cent stamp may be needed to balance out lost volume.

Congress currently is considering recommendations from a blue-ribbon commission on the future of the Postal Service, which called for a reduction in delivery to five days a week coupled with increased government subsidies and a serious attempt to add electronic transfer of mail messages.