The United States once again finds itself reacting to events in the Middle East rather than helping shape them. We can begin to shape events only if we launch a strenuous diplomatic effort in this period of emerging danger.

There are six main challenges for American diplomacy:

First, the United States cannot let Lebanon, as important as it is, monopolize the Middle East agenda. The Camp David negotiations will be set back, but it is crucial that the United States redouble its effort with Israel and Egypt to reach an agreement. Either the second half of the Camp David peace process must be implemented, with an interim agreement on full autonomy for the Palestinians of the West Bank and Gaza; or another peace process must be devised, but only if the Camp David talks fail.

Second, the United States must proceed urgently with the task of helping to reconstruct Lebanon. In the coming weeks, we will need to help install a credible peacekeeping force south of the Zahrani River--a fortified UNIFIL force, a Lebanese government force or another international force. We will also need to support the Lebanese presidential election scheduled this summer. The election is of enormous importance for a country whose unity and sovereignty have been put in question by Syrian, Palestinian and Israeli intervention. Our ultimate goal should be a free Lebanon for all Lebanese.

As we focus on the immediate human and political needs of all Lebanese, we must appreciate that a Camp David accord for the West Bank and Gaza, one which offers hope to the Palestinians, has to be at the core of any effective short- or long-term effort to reduce tensions in Lebanon.

Third, the United States must try to avoid the radicalization of the Arab states. Twin Arab defeats--destruction of the conventional military strength of the PLO in Lebanon and an Iranian victory over the Iraqi army on Iranian soil--could play havoc among the rulers of the Arab world. The discrediting of Arab governments that appear incapable of coping with regional and domestic problems could strengthen both the rejectionists, who have said that negotiations will never work, and the religious fundamentalists, who offer dignity and power to the downtrodden.

Our Arab friends will be under the enormous pressure of neighbors in the post-crisis environment to make accommodations with the realities they see in Iran, Syria, Libya and elsewhere. Even though the Saudis and Jordanians may have been upset with the PLO in recent months, they will be subjected to overwhelming pressure to close Arab ranks. American relations with the moderate Arab states are already strained and are likely to become more difficult. Our Arab friends will have to be convinced that out of the carnage in Lebanon can come a renewed movement toward a more durable peace in the region.

Fourth, the United States must try to persuade Israel to pursue peace with the same vigor and imagination that characterize its pursuit of war. American interests will require Israel both to quit Lebanon and to focus on peace talks.

The days ahead could be hard for Israel: a government with a slim majority may seek early elections; some Israelis are still reacting emotionally to the withdrawal from the Sinai; Israel will be resisting pressure to pull out of Lebanon until a satisfactory substitute for its armed forces is in place.

On the West Bank and in Gaza, Israel's 10- month-old effort to eradicate the influence of the PLO and promote another local Palestinian leadership has met with little success, but there will be some Israeli leaders who will want to give the effort a second chance during a period when the PLO in Lebanon cannot exert influence in the occupied territories.

Precisely because of its actions on the West Bank and in Gaza, actions that have raised doubts about Israel's commitment to United Nations Resolution 242 and to the peace process, it is in Israel's interest as well as our own to press on with the peace talks.

Fifth, the conflict in Lebanon poses challenges for American-Egyptian relations. The Egyptians want normal relations with Israel and improved ties with their Arab brethren. Thus, Cairo is disturbed that events in Lebanon tend to bolster the extremes and that the United States is either unwilling or unable to influence Israeli actions or to push for progress in the peace process.

The conflict in Lebanon casts into doubt Egypt's ability to play the role envisioned for it by the United States, that is, to sustain the peace along Israel's eastern front and to ensure stability in the Persian Gulf.

Sixth, the United States may find the Palestinians the most difficult of all groups to deal with in the Middle East. The options for the Palestinians and the PLO seem limited in the aftermath of the fighting in Lebanon.

Because the PLO is either unwilling or unable to recognize Israel's right to exist within secure borders without a simultaneous Israeli recognition of its rights, voices in the organization that have argued for some form of compromise and a two-state solution will be hard-pressed by defeat.

Radicals will argue for more terrorism and violence, tactics that the mainstream PLO leadership tried to minimize in recent years. The further radicalization of the Palestinian nationalist movement serves no one's interests in the Middle East, especially not Israel's. An effort must be made to engage in dialogue with a cross section of Palestinians, including leaders sympathetic to the PLO. The art of creative diplomacy in the Middle East will seek a way out of the current depression for as broad a cross section of Palestinian as possible.

The United States has a limited amount of time in which to influence the outcome of recent events in Lebanon. It is urgent that we give doubters in the region some reason to hope that peace talks can succeed. There is a critical linkage between events in Lebanon and the peace process. If we lose sight of the linkage, we will abet extremism in the region and damage important American interests.