Union leaders representing most of the Postal Service's organized workers reported "no significant progress" late last night in their contract talks with postal management.

The negotiators theoretically are working against a deadline of midnight tonight, when the Postal Service's current three-year contracts with four unions expire.

However, leaders of the American Postal Workers Union (APWU) and the National Association of Letter Carriers (NALC), which represent about 500,000 of nearly 600,000 unionized postal employes, repeatedly have sent signals that they are willing to bargain beyond the deadline if a settlement seems imminent.

Talks reportedly were going smoothly with the two smaller unions, the Mail Handlers Division of the Laborers' International Union and the National Rural Letter Carriers Association, meeting in Rockville, in separate bargaining sessions.

Only noneconomic issues were discussed over the weekend in the "main table" talks withthe APWU and NALC, who, under the supervision of federal mediators, are meeting with postal officials at L'Enfant Plaza Hotel here.

"We have made no significant progress . . . in those areas," APWU President Morris (Moe) Biller and NALC President Vincent R. Sombrotto said in a joint statement. "We regret to report that we are no closer to an agreement than we were when negotiations started three weeks ago."

However, the statement marked the first APWU/NALC "no progress" report in several days that was unaccompained by criticism of Postmaster General William F. Bolger or warnings of a possible strike. In the odd parlance of these particular negotiations, that indicated some progress, however minimal.

Assistant Postmaster General Walter E. Duka agreed.

"These are difficult negotiations. We make no pretense otherwise. But we are making some progress, and I still think we can have an agreement" by tonight's deadline, Duka said.

Duka said that, as of late last night, the Postal Service had not changed its request for a three-year wage freeze, made in negotiations Friday night. Biller and Sombrotto rejected that petition, calling it an insult to their membership. But Duka said Saturday, and repeated yesterday, that the wage freeze is required under provisions of the 1970 Postal Reorganization Act, which says the wages of postal employes must be based on comparability with workers in the private sector.

Comparability has been achieved, Duka said. He also argued that the Postal Service wage package contained a cost of living allowance (COLA) clause that would give postal workers $3,000 over the next three years -- if inflation continues at about its current rate. In effect, under the Postal Service plan, a higher inflation rate would yield postal workers no more than $3,000, since the COLA is "capped." A lower inflation rate would yield a lower return on the COLA.