This was supposed to be the week when nearly eight months of American diplomacy would attain its climactic goal - that long-dreamed-of and so-elusive day when Israelis and Arabs would agree to sit down together and begin the talks that would bring peace to the Middle East.
This was the week when, as so often before, it did not happen.
At the last moment, just as American diplomats thought they had an agreement buttoned up and everything ready for signing, the operation blew up.
The bomb that blew it up was thrown (figuratively, not literally) by the radical left wing of the Palestine Liberation Organization. PLO leader Yasser Arafat was forced to repudiate a formula he had worked out with King Hussein of Jordan. But behind the failure was a fatal flaw in the operation. The American government lacked the leverage that could in theory have brought success.
The State Department in Washington made a try at the last moment to provide the missing factor of leverage. It disclosed the substance of a letter from President Reagan to King Hussein. According to the State Department, King Hussein was assured by the President that if he agreed to enter into ''direct negotiations'' with Israel, to be based on UN Resolution 242, the US would respond by trying to persuade Israel to cease and desist from building more housing for Israeli colonists in occupied Arab territory.
Had the President's letter stated that the United States would insist on an end to the Israelis' building of new housing on the West Bank, the outcome could have been different. King Hussein has repeatedly said that he would enter direct negotiations and, by implication, would have Mr. Arafat's approval in the process, provided the US would guarantee an end to Israel's building program.
But the letter gave no guarantee. The wording was as follows: ''If Jordan publicly announces its willingness to enter such negotiations, we are determined to do our best to assure that the results of those negotiations are not prejudiced from the outset by activities of any party which reduce the prospects of a negotiated peace.''
But there is a world of difference between saying that the housing construction will cease and saying that ''we are determined to do our best'' to dissuade Israel from the construction.
A guarantee could have teeth if the White House would be willing to withhold economic and military aid to Israel. But the record is clear. President Reagan has been urging the Israelis since last September to cease building the housing. Earlier he had asked them to refrain from invading Lebanon. He asked them to limit that invasion once it had started. He urged them to a cease-fire. He has ever since the fighting ended last July been urging them to withdraw their troops from Lebanon.
But the President has never used the potential economic leverage of the US to enforce his urgings. And this week a subcommittee of the US House of Representatives voted an extra $365 million in US aid for Israel, with not a whisper of protest from the White House or State Department.
The promise to King Hussein is toothless when measured against the record. Mr. Reagan is unwilling or unable to put effective US pressure behind his promises to the King. Nor is he willing to authorize direct US talks with Mr. Arafat. Years ago, back in 1975, Henry Kissinger promised that the US would not deal directly with the PLO until the PLO recognized Israel's right to exist. The promise is not legally binding on anyone but Dr. Kissinger, but it has been observed ever since by Dr. Kissinger's successors at the State Department.
So once more, with the radical left of the PLO and the radical right in Israel cheering, peace has eluded the grasp of American diplomacy.
Mr. Arafat, having thrown the figurative bomb that blew up this week's peace prospects, flew off to Stockholm, where he assured Swedish politicians that the Reagan initiative was still revivable. This could mean that he wanted out from under the direct responsibility for blowing up the peace talks. It could also mean that he wants to provide time for Arab conservatives, primarily Saudi Arabia, to use the leverage they have over the PLO as a primary supplier of funds.
But Israel's deputy minister of labor and social affairs, Ben-Zion Rubin, announced plans to expand 68 settlements on the West Bank and in Gaza to accommodate an additional 20,000 Jews during the next 18 months.
In other words, the basic situation between Israel and its Arab neighbors is still dominated by the Arab radicals, who cling to the hope of sometime regaining all their lost lands, and by the Israeli radicals, who cling to their hope of gaining full possession of the whole of Palestine up to the Jordan River.
Forces in between would prefer a compromise and a partition of Palestine between Jews and Arabs. But the forces in between are still being outweighed and outmaneuvered by the radicals on both sides.
Elsewhere over the past week the Vietnamese armed forces in Cambodia launched a drive to wipe out the residual enclaves of resistance which have so far survived along the Thai border. China, which has been supplying and encouraging the resisters, has so far done nothing of substance to sustain the anti-Vietnam resistance. Without Chinese military help, the resistance would seem to be near the end of its road.
Also during the week, fighting flared up once more between Iran and Iraq. There was a substantial battle on the central front, with each side claiming to have inflicted heavy casualties on the other, but no substantial change in the front line.
President Reagan's Central American ventures on behalf of the government in El Salvador and the rebels in Nicaragua continued to draw criticism in Congress, but there were no serious results, either in the fighting in Central America or from the maneuverings in Congress.