THE DIPLOMATS are aflutter over the possibility that Indians will be offended and their nationalism aroused by the chance disclosure that President Carter is not at all happy with their government's refusal to accept "safeguards," against diversion to military use, on their peaceful nuclear facilities. The rest of us, however, can be grateful that Mr. Carter did not know his microphone was "open." He revealed that he is not taking Prime Minister Morarji Desai's "no" on safeguards as final. He's writing "another letter, just cold and very blunt." Since an impression was about that the United States was averting its gaze from India's continuing nuclear irresponsibility, this is good news, indeed.

Consider that the spread of nuclear weapons poses a danger to all nations. Consider that India has refused to sign the nuclear nonproliferation treaty. Consider that, since concern over proliferation became global, India is the one country to have cheated its way into nuclear status, exploding in 1974 a bomb it made by secretly diverting materials - including American heavy water - originally provided for peaceful purposes.To deter others from sneaking into the nuclear club, the United States should then have insisted that India accept international safeguards on all its nuclear facilities. Otherwise, Washington should have stopped supplying enriched uranium to the American-built reactor at Tarapur, even though it's safeguarded. Jimmy Carter was unequivocal on the subject during his campaign.

Once in office, however, he yielded to the argument that India's return to democracy, and its general political importance, required approval of the twice-a-year fuel shipments to Tarapur, pending passage of legislation to prevent exports of fuel (or facilities) to countries rejecting safeguards. In the interim, the administration decided to elicit a no-second-explosion pledge from India and to ask the Indians voluntarily to put their facilities under safeguards. Mr. Desai offered satisfaction on the first count. It was his failure to satisfy on the second that produced the remarks Jimmy Carter made in New Delhi. But the fuel, as previously agreed, is going through.

In the long run the principle of nonproliferation is unassailable, but in the short run the practice does not stand up well enough under competition from other diplomatic objectives. Someone will always find an immediate American self-interest in accommodating or cultivating the customer in question: India, Brazil, Iran, Argentina, Israel - you name it. One way conceived to ease politics out of nonproliferation policy was to establish the Nuclear Regulatory Commission to license peaceful nuclear exports. The NRC has helped, but its reach is limited. The fresh batch of fuel Mr. Carter promised the Indians the other day had not previously been cleared through the NRC, as it should have been. A second way is to enact the legislation restricting nuclear exports. The House passed this legislation unanimously last year. The Senate has been wasting time.