PRESIDENT CARTER disclosed his own Mideast peace plan on Wednesday, after seeing the Israeli prime minister but before seeing the Arab leaders. Notwithstanding the suddenness and his disjointed presentation, the plan seems to us extremely promising and sound, or as much so as one can expect in Mideast matters. The previous administration, after one false start, resisted offering its own plan, preferring to proceed by steps to interim measures and then into a "process" of peace-seeking. That process, of course, was stalemanted. Mr. Carter evidently decided that the best way to get Arabs and israelis to face the difficult concessions both will have to make for peace was to set out his plan right off.

It calls for a lined exchange of almost all the territory Israel acquired in 1967 (save for "minor adjustments") for equally sweeping Arab political concessions. The territorial aspect delights the Arab, who equate peace principally with recovery of land. It dismays the Israelis. Mr. Carter, however, accepts the Israeli definition of peace: "a termination of belligerence toward Israel by her neighbors; a recognition of Israel's right to exist; the right to exist in peace; the opening up of borders with free trade, tourist travel, cultural exchange between Israel and her neighbors." Israelis regard these elements as the essential evidence of Arab willingness to accep Israel as a permanent and legitimate neighbor. Arabs wish, in the words of Egyptian President Anwar Sadat (a moderate on this issue), to leave these elements to "the next generation." Obviously, it is by offering each side what it most wants that Mr. Carter hopes to induce it to offer the other what it most wants. It is a gamble. It is also, in our judgment, the only way.

To reduce the gamble, President Carter is thinking of a broad and novel transition over "two years, four years, eight years, or more." He proposes Israeli "defense lines" beyond the "permanent and recognized borders" to be negotiated. This "Israeli defense capability" might include, besides "the sometime placement of Israeli forces," international forces, monitoring stations and demilitarized zones. Though he had so hinted earlier in the week, Mr. Carter does not accept "defensible borders" in the sense that the phrase has come to mean Israeli retention of large chunks of formely Arab territory. But he does accept that Israel's security requirements, for which the United States has long accepted a special responsibility, must be squarely addressed.

Much remains to be learned about the Carter approach. He referred only in passing, for instance, to the critical Palestinian question, currently the object of intense Arab maneuvering. We think, nonetheless, that Mr. Carter is right to make a bold Mideast initiative and that his effort is serious and fair and deserving of the most responsible consideration by the parties in the Middle East and by the American public as well.