PRESIDENT CARTER, by putting off his rather zany foreign trip, has done a good bit more than create the opportunity to put together a more sensible journey at a later time. He has allowed himself to bring the full powers of the presidency to bear on his energy program, currently in a parlous position on Capitol Hill. Moreover, in doing that he has sent, to those foreign governments keen enough to realize it, a message far more important than any he might have delivered on a 9-country, 12-day spin around the globe. The message is that, for Jimmy Carter, first things come first. Those first things are the passage of the most important legislation he is demanding of the Congress this year, and the consequent demonstration - if his effort is reasonably successful - that he is President able to work his will in a central and contentious area of public policy.

The wonder is that, to judge by news reports, there are some foreign observers and even some American diplomats who see the postponenment of this trip as a mark against the Carter administration. We think it obvious that those who see the rescheduling as "amateurish" are themselves being lamentably amateurish in failing to understand that a President's greatest asset is his political credibility, which can be established only at home. What good does it do to chief executive to speak fancy or hopeful words abroad if he is simultaneously being seen to shy away from necessary domestic battle or to wage it ineffectively? As for those American diplomats who fear that the postponement will be taken as a sign that Mr. Carter values domestic considerations over foreign ones, they deserve to be sentenced to reach each other's memos. No foreign policy worthy of the name can be constructed on a crumbling domestic base.How can this particular lesson of Vietnam have been forgotten so soon?

It is worth recalling that the substantive as well as the political thrust of Mr. Carter's energy program is eminently international. It is a program designed, above all, to reduce American dependence on "uncertain" foreign energy sources and thereby to help the United States conduct a more effective foreign policy. If foreign friends, foes and opportunists alike see that the United States is not serious about enacting a program of energy conservation and development of alternative domestic supplies, they will invariably - and accurately - draw negative conclusions about the United States' strength and reliability and capacity for a world role. Mr. Carter, in announcing his energy program, had termed it "the moral equivalent of war." If that's how he feels about it, he could hardly be expected to desert under fire.