THE SECRETARY of the Interior, James G. Watt, has made himself a reputation as a man capable of foolish and harmful public statements. It now develops that his private statements can be even more askew. In a letter last month to the Israeli ambassador, he suggested that "the liberals of the Jewish community," should they persist in opposing the Watt energy policies, will "weaken our ability to be a good friend to Israel." The White House hastily termed the letter "unfortunate." How true.

First, for the simple misstatements of technological fact--we'll get around to the truly disgusting part in a minute. "If we do not reduce America's dependency upon foreign crude energy," Mr. Watt wrote, "there is great risk that in future years America will be prevented from being the strong protector and friend of Israel that we are and want to be." Those lines faithfully reflect the oil-field fantasy that, if the drilling crews could just get those environmentalists out of their way, the industry could rapidly make the United States self-sufficient in oil --relieving Americans of the necessity of paying any attention to the Arabs.

The relationship to reality is zero. This country still imports about one-fourth of its oil, and the industry will have to do a lot of very expensive drilling simply to keep domestic production up to the present level. Even if the United States were self-sufficient, its allies and customers in Western Europe and Japan remain heavily dependent upon the Persian Gulf.

But that's merely a factual matter, and the least of it. There are more objectionable suggestions in Mr. Watt's letter--greatly more objectionable. One is that U.S. support of Israel is somehow contingent on a plenitude of oil for American consumption, that our support of Israel, in other words, is a kind of luxury or frill we will maintain only so long as the oil flows from someplace. The other is that it is the obligation of American Jews to support certain administration policies and that it is appropriate--or even decent--for a Cabinet officer to threaten an abandonment of Israel if they don't. Does Mr. Watt think of American Jews as foreign nationals? Does he really believe there is nothing wrong with the idea that the way to reach them is through a communication to the embassy of Israel?

Mr. Watt's usefulness to this administration, let alone his public standing in any larger sense, was never great. It now sinks toward the vanishing point.