DISCRETION may not be the better part of nuclear non-proliferation, but it is a helpful part and, in the Middle East, it has suffered two harsh blows since Israel destroyed Iraq's reactor. First, Iraqi President Saddam Hussein went public with an appeal to foreign countries to help Arabs build a nuclear weapon "to confront Israel's existing bombs." Israel's former defense minister Moshe Dayan followed by giving Israel's most authoritative report to date on its nuclear status, saying that his country has the capacity to produce a bomb on brief notice.

For President Hussein to put forth a rationale for building a bomb and to ask for aid makes a joke of Iraq's acceptance of the Nuclear Non-Proliferation Treaty. That same attitude characterized his responses yesterday to Barbara Walters' tough and purposeful questioning on ABC-TV. To be sure, there is somber evidence that before the raid Iraq was cheating on the treaty and was making plans to put together a bomb -- notwithstanding President Hussein's evasions yesterday. Yet the treaty, and the safeguards designed to enforce it, have provided a certain opening by which international non-proliferation elements could bring their admittedly inadequate influence to bear. Now even that opening seems to have been narrowed. The Israeli raid, humilating Iraq as it did and demonstrating the importance the Israelis place on maintaining a nuclear advantage, furnished a certain impetus for Iraq to take to the public nuclear road.With his statement, his first since June 7, President Hussein has gone far to lock himself in.

It was left to the ever-confounding Moshe Dayan, however, to top him. Gen. Dayan's statement that Israel is in effect only one screwdiver away from a bomb was truly mischievous. Few people may have doubted it; many think Israel already has bombs ready. For someone of his presumed knowledgeability to flaunt Israel's near-nuclear capability, however, ratchets every Arab's rage and alarm one huge notch forward. It was as though Gen. Dayan had deliberately set out at once to ensure that Iraq would get (back) on the track of a nuclear bomb, and to create broad international understanding for its nuclear ambitions.

Ideally no Middle East country would have a bomb, or would be working on one, or would be a screwdriver away. But that paradise was lost long ago. Ideally after that, any country with nuclear competence or ambition would go about it carefully and discreetly, so as not to provoke its adversaries into a matching program. This is the useful veil that has been ripped away, twice, in the last few days.