Although President Carter pushed the command button on Sept. 16 it could be February or even June before federal agencies begin doing what he said, which was for them to hire more part-time workers.

The problem is an old one in Washington. It is part mechanical and part political. Telling people to do something is easier than telling them how to do it; or how badly you really want it done.

Federal agencies can, and do, hire part-timers. The government has about 200,000 people who work for it everything from temporary letter carries to forest workers, summer aides and vacation replacements.

But Uncle Sam has only 39,000 "permanent" part-time employees. Most work from 20 to 39 hours, and they usually have fixed schedules and draw equivalen civil service benefits like insurance and vacation.

The reason there aren't more permanent part-time employees is because Congress and the White House set personnel ceilings for agencies. Since part-timers count the same as full-time workers, most managers reason they would rather have somebody in a 40-hour job than "waste" that slot on a part-timer.

The political reason there aren't more part-timers, and may not be more for some time, is the same. Numbers. President Carter (like Ford, Nixon, Johnson, Kennedy and Eisenhower to mention just a few) campaigned on making government leaner and more efficient. A large influx of part-timers would boost the totals in agencies and make it appear that government was growing faster than it really was, and contrary to all those lean and tough promises.

President Carter says he wants the government to provide more job opportunities to the elderly, housewives, students and others who can't, for one reason or another, work a full 40-hour week. He thinks the government would benefit as much as the people who get the part-time jobs. He is probably right.

But federal agencies are - and will remain - reluctant to hire part-timers because of the head court system. They don't want to lose spaces for full-timers and they don't want to get the President (and themselves) into political hot water by overstepping those ceilings.

There is a solution that both the executive branch and Congress are working on. It involves a new book-keeping system that would permit jobs to be counted as they are now, and also to be counted fractionally, based on hours worked. This man-hour counts is coming, but officials say it will be three to six months before it is "in place." And it might require more employees - perish the thought - to do it.

Office of Management and Budget is working on the man-hour accounting system. The Civil Service Commision soon will identify agencies - probably three or four - where it will be tested on a limited basis. But that will take time.

Best advice for people seeking part-time work with the government is to keep looking and sending in those forms. But don't count on getting anything in time to help with Christmas shopping, or even with your income tax bill that comes due in April.

It is true that the button has been pushed; but the message won't be acted on for sometime.