It's back to the drawing board now for the Reagan administration in Washington. Its existing plans for handling its two most important and difficult foreign policy problems - the Middle East and Central America - are not working.
The Middle East plan has in effect been torpedoed by Yasser Arafat, Menachem Begin, and whoever planted the bomb which blew up the United States Embassy in Beirut. The US is no longer in a position to broker a ''comprehensive peace'' for the Middle East.
The Central American plan is bogged down in tenacious opposition in the Congress, disapproval from much of Latin America and from the NATO allies in Europe, and the lively fighting qualities of the rebels in El Salvador.
The idea of saving El Salvador from communism by guns and by backing counterrevolutionaries in Nicaragua begins to look to almost everyone outside the ranks of right-wing Republicans like a no-win strategy.
But the problems which gave rise to the plans remain.
President Reagan cannot afford to let the Soviets develop new political and perhaps also military positions in Central America.
Nor can he afford to stand by watching if most Arabs, even the ''moderates,'' frustrated by the failure of the Middle East ''Reagan plan,'' look to Moscow for help.
There must be new plans devised for both the Middle East and Central America.
In the Middle East the urgent need is for some new device that will persuade the Palestine Arabs that they can get more from the West than they could get by turning to Moscow.
The essence of US strategy toward the Middle East has been just that - the contention that Washington can do more for the Arabs than can Moscow.
That was the premise which Henry Kissinger sold to Anwar Sadat of Egypt. It was the central feature of the Camp David formula, which brought peace between Egypt and Israel, and of the ''Reagan plan'' put forth by the American President last September to continue the Camp David process.
It was spelled out in the Reagan plan.
And according to King Hussein of Jordan, it was spelled out in fuller detail in the President's most recent communications to the King. The President allegedly promised the King that he, Mr. Reagan, would get the Israeli troops out of Lebanon and persuade the Israelis to accept a partition of Palestine between Jews and Arabs.
But in the long months since the formulation of the Reagan plan, the President has been unable to persuade the Israelis to withdraw from Lebanon or to cease and desist from building more housing for Israelis in Arab territory.
The strategy which Mr. Kissinger initiated has survived up until now on the basis of its original success. When practiced by Mr. Kissinger and by his successors during the Carter days, it did win back the whole of the Sinai Peninsula for Egypt. Egypt did reclaim its lost territories through Washington, not through Moscow.
If it worked for Egypt, then, so the theory ran, it might also work for Jordan, for Lebanon, and for the Palestinians.
But President Reagan was unable to bring enough leverage to bear on Israel to make it work for Lebanon and for the Palestinians.
Therefore we are now at a point where Syria has asked, and been given, the new and latest Soviet antiaircraft weapons and Soviet soldiers with them to make sure that they operate effectively. And other Arabs are wondering whether perhaps Moscow might be called in in other ways to sustain them against Israel.
Yet good relations with all the Arab states are considered important both in Washington and in all the capitals of Western Europe. The Western alliance cannot afford to alienate or lose the goodwill of the Middle East. There has to be a new beginning, and its prime purpose must be to work out something better for the Palestinians than the prospect of being squeezed out of their own native homeland by the Israelis.
This is where Mr. Reagan's planners have to start over.
As for Central America, US Secretary of State George Shultz was in Mexico City during the past week. He had two days of talking with his Mexican opposite number, Bernardo Sepulveda Amor. A communique issued at the end of the talks said that the two men discussed Central America and ''agreed to promote processes of dialogue and negotiation for the purpose of avoiding armed conflict.''
If Mr. Shultz actually pursues a policy of ''dialogue and negotiation'' as a means of avoiding ''armed conflict'' in Latin America, he will be reversing the strategy adopted at the White House on April 6, 1982, and still being pursued.
That strategy called for direct, overt military aid to the government of El Salvador, coupled with covert support for counterrevolutionaries in Nicaragua. Another part of the 1982 strategy was to keep Mexico and Social Democrats in Europe ''isolated on Central American issues.''
The Shultz talks in Mexico City do not in themselves abandon the 1982 strategy and begin a new one. But the talks do label an alternate policy which could be used if and when the President is willing to abandon the 1982 strategy of arms and CIA covert operations.
The Foreign Affairs Committee of the House of Representatives this week voted 19 to 16 against an additional $50 million in military aid for El Salvador this year. The vote is not decisive on the subject and will not prevent the White House from continuing for yet a while with its arms-rather-than-talk strategy.
But that vote does measure a rising uneasiness in Congress about the arms policy toward Central America. And the latest reports from the fighting fronts in El Salvador would seem to indicate that the rebels are improving their military performance faster than are the government forces, even with US weapons and US training.
Unless the 1982 strategy begins to show impressive results fairly soon, it seems likely that Congress will require a switchover to the strategy of the Mexico City communique.