IN UNDERTAKING TO RESTART the Egyptian-Israeli peace talks, the United States is showing a good understanding of one reason why they stalled a month ago. They stalled after the administration 1) gave the appearance of having stepped out of its Camp David role of mediator by giving its endorsement to the position of one side, Egypt, and 2) allowed the target date of Dec. 14 to harden into a deadline, which became a club used (unsuccessfully) against Israel. In the intervening month, American officials have eased back into public evenhandedness and a pace respectful of complexity. A State Department mission is in Jerusalem and Cairo to reopen talks, and while there is an urgency to American diplomacy, no dates on the calendar have been ringed.

The administration is eager to press on but no less eager to aviod another and conceivably fatal setback in the talks. Thus the current mission is focusing on "minor problems" -- the privision for future review of the treaty and the question of the relative weight of Egypt's obligations to Israel and to other Arabs.The next stage would be to raise discussions to the level of foreign minister. President Carter put a crimp in this plan on Sunday by endorsing the prospect of another summit; Governments facing a summit are not easily tempted to deal cards away in the foothills. The trick remains to convey to Israel and Egypt that Washington stands ready to help them reach an agreement, if they are prepared for the new approaches that alone will make an agreement possible.

The central point on which a new approach is mandatory is the link between an Egyptian-Israeli treaty covering the Sinai, and an agreement on Palestinian self-rule in the West Bank. Responding to Arab accusations of selling out the Palestinians, the Egyptians last month demanded a tight link. The Israelis, unprepared to make a treaty with Egypt hostage to a West Bank negotiation that no Palestinian is now willing to join, insisted on a loose link. Last month the United States supported Cairo. If there is no change, the Camp David process appears dead.

The new factor -- the X factor -- is Iran.Has the turmoil there made Israelis and Egyptians (and the influential Saudis) more interested in completing a treaty by way of trying to stabilize at least one sector in an increasingly turbulent region? Or has Iran made Israel less willing to meet a neighbor halfway, and Egypt (and the Saudis) less able to buck a running Islamic tide? It's uncertain. One of the larger tasks of American diplomacy is to convince the parties that the Iranian upheaval can only mean trouble in the area and that their best protection lies in moving toward and Arab-Israeli peace.