Postmaster General Benjamin F. Bailar is expected to win approval Wednesday from the U.S. Postal Service board of governors for a formal request that would seek higher postages rates in 1978.

He is expected to propose an increase of 3 cents an ounce for first-class mail to 16 cents.

Postal management also has been studying an end to mail deliveries on Saturday, which could keep the first class rate boost to 2 cents, if adopted.

Given outspoken opposition on Capitol Hill to proposals for elimination of six-day-a-week deliveries, however, the higher first-class rate proposal apparently is being favored.

By a voice vote of 77-7, the Senate recently supported a proposal by Sen. Robert Dole (R-Kans.), in favor of maintaining Saturday delivery. A reduction in mail service to five days "would have a detrimental impact on rural newspapers," Dole stated.

The Postal Service board must approve rate or service cutback proposals, which then would be submitted to the independent Postal Rate Commission for approval or rejection within 10 months.

President Carter told his news conference Thursday that he has not yet made a decision on administration policy about the Postal Service's future. After the board acts on the rate proposal, he said, "it would be an appropriate time" to comment.

According to The Wall Street Journal, one plan being studied by Carter would be a cheaper first-class mail rate for individuals than for business: a White House staff proposal reportedly suggested two first-class stamps for a quarter.

Meanwhile, Bailar revealed that the Postal Service completed the year ended June 30 with a deficit of about $50 million, compared with a loss of $1.2 billion the previous fiscal year.

Although these figures do not reflect government subsidies paid to underwrite money-losing operations, Bailar said the figures show "real progress." He declared the Postal Service to be in the best operating and financial condition since it was created on July 1, 1971.

Part of the improved operations can be traced to a reduced work force of 657,000, down to 84,000 from a high of 741,000 before the transformation of Postal Service from the old Post Office Department in the executive branch. He said 96 per cent of mail eligible for overnight delivery is being delivered on time.