Efforts to resume deadlocked negotiations yesterday between the U.S. Postal Service and two unions were set back almost immediately when the 250,000-member National Association of Letter Carriers said it would not participate until Postmaster General William F. Bolger appears for the first time at the bargaining table.

"We have received no indication that Postmaster General Bolger is willing to come to the table himself to bargain over the critical economic issues that caused this impasse -- wages and benefits. Therefore, I shall not be returning to negotiations," NALC President Vincent R. Sombrotto said.

Bolger, who was not available for comment, said 10 days ago that he was eager to resume long-stalled negotiations, saying on "Face the Nation" (CBS, WDVM):

"I think we ought to get back to the table. I think I'm ready, willing and able this afternoon, if need be, to send my spokesmen back to the collective-bargaining table."

Bolger's statement was among factors that led to yesterday's attempt to resume bargaining with the NALC and the American Postal Workers Union, which represents 320,000 employes. But Bolger, who plans to retire in December, had not committed himself publicly to appear personally at the talks. USPS spokesmen would not discuss the issue.

APWU president Moe Biller, who had called Bolger "gutless" for not participating directly, said yesterday that he is eager to meet with Bolger but, "At this moment, nothing is scheduled."

Lawyers for the Postal Service and unions met yesterday to set ground rules for resumption of the first negotiations since talks broke off July 20, when the USPS's three-year contract expired. It was unclear whether talks would resume on the key economic issues.

The USPS is proposing a three-year wage freeze and a 23 percent pay cut for new hires. Postal workers earn an average of $23,000 yearly. If the talks do not resume, the entire contract, by law, is to be submitted to a three-member arbitration panel, which is to review both sides' presentations and make a binding decision.

Postal strikes are illegal, and the two unions voted at conventions last month to allow the arbitration process to proceed before deciding on any possible actions. Despite misgivings about an illegal strike that could result in mass firings, members authorized Biller and Sombrotto to call strikes under certain circumstances.

In a related matter, John R. McKean, chairman of the Postal Service Board of Governors, said at a governors' meeting yesterday that planned postage increases approved by the Postal Rate Commission last week will not take effect until next year.

The independent commission approved various increases, including rises in first-class postage from 20 to 22 cents and in the postal card rate by a penny to 14 cents. The increases were less than the Postal Service originally requested.

Postal officials said the increases are not needed immediately because a lower rate of inflation has reduced labor costs from earlier projections and because higher mail volume has increased revenue.

The governors, who had sought a 23-cent first-class stamp, took no formal action on the rate commission's recommendation. The nine governors can accept the decision, ask the commission to reconsider, appeal it to a federal court, or overturn the decision by unanimous vote.