A showdown on the issue of lower wages for newly hired employees appears to have been averted for now in the US Postal Service. Major unions representing more than 500,000 postal workers, responding to congressional action that blocked a two-tier wage policy in post offices, put aside strike threats and accepted binding arbitration in their contract disputes with management.
Separate conventions under way in Las Vegas, Nev., at the same time, however, warned that unions are leaving options open for militant action if postal management ''reneges on its commitment to obey the new law or tries again to cut wages and benefits.'' The ''new law'' requires fact-finding and binding arbitration of labor disputes involving the US Postal Service, funded in part by the US Treasury.
The National Association of Letter Carriers, with 200,000 members, voted to submit its contract dispute to binding arbitration. But its president, Vincent Sombrotto, said bluntly that if management does not accept aribtration or tries to put into effect wage and other changes unilaterally, then ''I have been given the power to call a strike.''
The American Postal Workers Union, representing 300,000 unionists, avoided any strike action and gave Moe Biller, its president, ''total flexibility'' to respond to any management moves to circumvent binding arbitration or to make wage and benefits changes before arbitrators can issue a binding decision this December.
The warnings are more routine than actual threats. Delegates to the two conventions complained bitterly about Postal Service demands for ''takeaways'' that they said would undermine Post Office pay scales and threaten their unions.
But there appeared to be little sentiment for strikes that could jeopardize their jobs. Most unionists were mindful of the dismissals of airline controllers when they struck illegally.
Postmaster General William Bolger recently warned that any postal employee who strikes illegally would be dismissed and barred from future federal employment.
Mr. Biller and Mr. Sombrotto favor binding arbitration.
The Postal Service is also expected to accept arbitration of its demands for labor cost savings to bring its wages and benefits more into line with those in private employment.
A failure to do so after the unions' acceptance of arbitration would place any blame for mail disruptions on the Postal Service and create new problems with a Congress that has just blocked lower wages for newly hired postal workers.