Never-say-die Reagan administration officials are still confident that they can sell Congress parts of the controversial federal retirement "reform" package, despite its lack of influential supporters.

The fact that the plan, which would raise the federal retirement age and increase employe payments to the civil service retirement fund, still has not been introduced in Congress doesn't mean it is dead, according to administration strategists. That means they either know something or are viewing the world through rose-colored glasses.

If the reforms became law, federal employes (who can now retire at age 55 after 30 years' of service) would take a steep annuity reduction of 5 percent a year for each year they retired under age 65. The proposal, outlined in the president's budget, would also force employes to put 9 percent of their salaries into the retirement fund next year, and 11 percent beginning in 1985. Employes now contribute 7 percent to the civil service fund.

The proposal has frightened and angered many civil servants.

Democrats in Congress have denounced the proposals. Important Republicans, like Ted Stevens, assistant Senate majority leader, also oppose the changes, which have upset their federal constitutents.

Unions representing federal and postal workers, which lost the fight to keep new government employes outside of social security, have made killing the reform plan their top legislative goal.

Given that reception, one would think the administration might decide it had enough on the congressional plate and hold back the plan for another time.

But administration officials say the bill will be introduced this year, and, if necessary, next year, and so on until they win.

One part of the bill that backers think they can win this year deals with outlays for federal retirement. The administration wants to put a permanent limit on cost-of-living adjustments (COLAs) for retirees who are under age 62.

Congress tried to do that last year by limiting the "younger" retirees to smaller raises in 1983, 1984 and 1985. But Congress overestimated the rate of inflation, which determines the size of COLA. As a result, retirees who are 62 and younger got a 3.3 percent COLA this month, while older retirees got a 3.9 percent raise.

Administration officials want--and think they can get Congress to accept--language that would give the younger retirees only half of the COLA raise each year. If that plan were in effect now retirees who got a 3.3 percent raise this month would have gotten only about 1.9 percent.

"Really, that is where big savings can be made immediately," an official of the Office of Personnel Management said yesterday. He noted that Congress has already accepted the principle of half a COLA for the younger retirees, even if it made a mistake by setting a minimum increase for them.

Under current law, federal retirees age 62 and under are guaranteed a minimum 3.6 percent next year, even if the actual cost of living is less than that amount. Those same retirees are guaranteed a 3.3 percent raise in 1985 because of the minimum Congress built into the legislation. In fact, even if the cost of living declines, those retirees (whom Congress considers better off financially than their older counterparts) would get the guaranteed minimum.

"We want it all," an administration official said of the retirement reform package. "If we don't get all of it this year--and we expect to get something--we will come back next year, and the next year and the year after until we get it."