President Reagan's assurances to Israel that the United States will continue to support Israel's ''qualitative'' edge in weaponry over Arab states appears to have satisfied Prime Minister Menachem Begin.
A senior Israeli official said Wednesday the letter - which discounted the possibility the Reagan administration would sell F-16 jets and mobile antiaircraft missiles to Jordan - ''was more or less in line'' with Israeli wishes.
Special US negotiator Richard Fairbanks arrived in Israel Feb. 17 for four days of meetings before visiting Egypt next week.
An Israeli official says Israel wants an autonomy agreement before April 25, when it evacuates Sinai. Egypt, however, remains reluctant to rush into an agreement.