Suddenly, a plan for a Middle East peace arrangement which the Saudis first put forward about three months ago has become the center of discussion and debate.
It has become highly controversial. The State Department in Washington has expressed interest. But Prime Minister Begin of Israel calls it a plan ''to liquidate Israel by stages'' and argues that it would impede the Camp David process.
What is this all about?
There is nothing new in the Saudi plan except that it sketches out in some detail the implications of the basic document which has been the foundation of all attempts since 1967 to end the 30-year war between Israel and its Arab neighbors.
That basic document is United Nations Resolution 242 which was adopted, unanimously, in the Security Council of the UN on Nov. 22, 1967. It had been drafted by the British delegation at the UN in consultation with the United States delegation which, in turn, had consulted the Israelis. It had the acceptance of Israel at the time.
It is brief, and explicit. It has two paragraphs only that really matter. The first calls for ''withdrawal of Israeli armed forces from territories occupied in the recent conflict. . . .''
The second calls for an end to the fighting and '' . . . acknowledgement of the sovereignty, territorial integrity, and political independence of every state in the area and their right to live in peace within secure and recognized boundaries free from threats or acts of force. . . .''
The Saudi plan restates the two basic provisions of 242 and adds dismantling of Jewish settlements in the occupied territories, establishment of a Palestinian state with East Jerusalem as its capital, and compensation for refugees who do not return to their homeland.
The addition of the first two points is unnecessary. If Israel withdrew its armed forces from the occupied territories most Jews who live in the settlements would probably go back with the Israeli troops since their presence inside an Arab community would be less than comfortable. Some few might remain under special arrangements with the local Arab community, but not as members of a foreign enclave. The Jewish settlements as such would disappear.
As for East Jerusalem. It is ''occupied territory.'' Its population is overwhelmingly Arab. It was the political and cultural Arab center previous to the Israeli occupation in 1967. It is the hub of the road network on the West Bank. It is the logical place for the capital of an Arab state, if one comes into being. If it is evacuated by Israeli troops it will logically become again the political center for the liberated Arab community.
Also, whether there is to be an Arab state in the liberated territories need hardly be spelled out in any plan. The single essential issue is Israeli withdrawal. If there is a withdrawal then the Arabs of the occupied territories are on their own and can do what they please about a political organization. They could choose to rejoin Jordan, or set up their own government.
Thus the essence of the ''Saudi plan'' is identical with the essence of UN Resolution 242.
Presentation of the Saudi plan at this time does not ''impede'' Camp David unless one assumes, as some critics of Camp David do assume, that the process had become a device through which Israel might evade the substantial withdrawal from occupied territories intended and required in Resolution 242.
The Camp David process is slow. Prime Minister Begin has repeatedly declared that he will never give up ''Judea and Samaria,''which means the West Bank. Presumably he has assumed that so long as he was negotiating under the US-supervised process of Camp David he would be able to avoid full compliance with UN 242.
In that sense the presentation of the Saudi plan at this stage might speed up rather than impede progress toward withdrawal of Israeli occupation troops from the occupied territories.
In other words we are back to the basic issue, which is territorial. Is Israel to go back to its pre-1967 boundaries (with minor adjustments to be negotiated)? Or is Israel to keep and consolidate and add to the territories of Israel those occupied territories which are inhabited by more than a million Arabs who will never accept such annexation peacefully?
Another way of stating this is whether Washington will connive with Israel at thwarting the intent of UN 242, or stand on 242 in fact as well as theory?
Mr. Reagan has a difficult choice ahead of him.