The State Department, which plans to eliminate about 1,270 jobs because of severe budget cutbacks, said yesterday that it has been given permission by the Office of Personnel Management to offer voluntary early retirement to its civil service employes.

Department spokeswoman Phyllis Oakley said as many as 500 persons may be eligible for the offer.

Department officials, anticipating a shortfall of about $84 million in the fiscal 1987 operating budget it gets from Congress, is preparing far-reaching cuts, from consolidating offices within the department to closing two small embassies and 13 consulates.

However, the core of the retrenchment program will involve trimming up to 1,300 Foreign Service and civil service jobs, most of them in Washington, through a combination of early retirements and, if necessary, a reduction in force (rif) that would mean involuntary layoffs.

Department officials are expected to ask Congress to amend the law governing the Foreign Service to permit both early retirement incentives and a rif. Existing law allows the department to apply such measures to civil service employes if OPM concurs.

Oakley said the early-retirement offer will apply to employes of any age with 25 years of service and employes age 50 and over who have 20 years of service. They will be offered retirement benefits they normally would qualify for at age 55, minus a permanent 2 percent reduction for each year of age under 55. Not eligible for the offer are secretaries, auditors and engineers, because the civil service has shortages of such personnel.

Another aspect of the austerity program became evident last week when the department halted its longstanding practice of making press officers available on a 24-hour basis to respond to reporters' queries about late-breaking news.

The step was made necessary by a decision to eliminate overtime pay to the six press officers. However, the department has promised that during periods of international crisis, it will have press officers available around-the-clock.