Pentagon pressure has temporarily blocked a budget-cutting proposal to limit growth of the multibillion-dollar federal and military retirement package by limiting pensioners to a single cost-of-living raise each year.

That means retirees who had feared that the cutback would be made this year will get inflation catch-up raises on March 1 and in September. They are designed to keep the 2 million-plus retirees abreas of rising living costs. It is the nation's largest pension plan, and one of the few indexed to the inflation rate with guaranteed upward adjustments every six months.

The White House, as late as last week, had planned to ask Congress to eliminate one of the two annual raises. It would have had the effect of cutting each retiree's future pension raise an average of about 2 percent a year.

Backers of the single annual adjustment had good economic (and political) arguments on their side. They pointed out that ex-federal workers and military personnel are much better off than non-federal retirees because of the twice-yearly adjustments. Eliminating one of them would have cut costs both administratively and by eliminating the compounding factor one raise has on top of another.

Politically, the plan probably would have been popular. It would have saved -- officials say -- millions of dollars in a short time. And it would have represented the sort of kick-in-the bureaucracy's pants that the new 96th Congress believes it was elected to administer.

The plan to eliminate either the March or Septemeber raise was very much alive in early December when the Federal Times reported it. But protests from federal and military retiree groups, unions and the active duty military rolled into the Office of Management and Budget. That was just before the plan was to be cleared as part of the budget President Carter will send Congress next week.

Insiders say the military arguments persuaded OMB and the White House to stick with the present twice-yearly raises -- for the time being. Army, Navy and Air Force leaders, military and civilian, argued that the military retirement system is facing enough changes. It would be unwise, and unfair, to cut it now. If you must change it, they told budget planners, leave the military retirees under the March and September annuity adjustment system even if civilian retirees are limited to one raise.

Officials felt it would be unfair to keep the military under a twice-yearly raise system, while limiting civilians to one raise annually. Besides, the present system is itself a compromise for a benefit cutback in the last few years.

Federal-military retirees formerly got cost-of-living raises that included a 1 percent "sweetner" That got too expensive. Congress took away the 1 percent add-on instead guaranteeing retirees regular adjustments every six months based on straight cost of living.

So the present system will be around, at least for this year. The first 1979 raise is effective March 1. It will show up in April checks, and be worth at least 3.3 percent. The second 1979 raise comes in September, payable in October. Word that the two raises are to be left alone should comfort retirees, and make it easier for those who must file quarterly estimated earnings statements with the IRS.

According To The Polls... Federal employe unions have borrowed a technique from Democratic and Republican politicians, They are using pollsters to help their case and rattle the other guy. Recently the American Federation of Government Employes polled more than 400 Department of Energy workers, asking their view-points on a number of work-related issues. The AFL-CIO union is squared off for a representation election that will take place today between it and the independent National Treasury Employees Union (NTEU).

According to the AFGE survery, 50 percent indicated they would back it in today's vote. The remainder split between voting for "no union" and the NTEU. Results will be out shortly.

Meantime. the NTEU has won exclusive bargaining rights for 500 field workers of the Nuclear Regulatory Commission. It beat its "no union" opponent 2 to 1. The NTEU has expanded orgasnizing and membership outside Treasury and now represents workers in several different agencies.