Washington — In deciding to extend the controversial draft registration program, President Reagan is finding that a commander in chief's decisions must sometimes countermand a politician's promises.
As a presidential candidate, Mr. Reagan repeatedly opposed the drafting of young men into the military and even their registration for possible future conscription.
''The most fundamental objection to draft registration is moral,'' Reagan said in 1980. ''Only in the most severe national emergency does the government have a claim to the mandatory service of its young people.''
The administration continues to hope that recent military pay increases will attract the several hundred thousand persons needed to make up the shortfall in military personnel. But the Joint Chiefs of Staff still are not satisfied that the all-voluntary military will meet their needs, and have convinced Defense Secretary Caspar W. Weinberger (who also had opposed the draft) of their view.
Mr. Weinberger headed the military manpower commission that recommended the continuation of the draft.
Current trouble spots around the world -- particularly Poland -- thus have given draft proponents at least a temporary advantage in the national debate on the subject. At a time when the President is urging the European allies to take a harder line against the Soviet Union on Poland, it would have been difficult for him to give the impression that he was less than firm with his own armed forces. Several of the Western allies, including West Germany, do require military service of their young men.
Announcement of the President's decision on the draft may not be as politically damaging as the breaking of a campaign promise often is, however. According to the Gallup poll, 71 percent of those polled favor national service or required civilian work for young men between the ages of 18 and 24.
As might be expected, those who could be drafted are less enthusiastic. Of the 7.4 million young men currently eligible for draft registration, 800,000 have failed to sign up. Former President Jimmy Carter had called for such registration following the Soviet invasion of Afghanistan two years ago.
Whether those who have failed to register now will do so, or whether the federal government will proceed with their prosecution, remains to be seen.