George Shultz's visit to the Middle East has put United States credibility squarely on the line. That at least is the view that was being expressed by many Arab officials, most notably Egyptians, as the American secretary of state arrived here Monday to begin a trip of undetermined duration around the region.
The United States, they say, repeatedly promised during the past five months that Israeli, Syrian, and Palestinian forces would soon pull out of Lebanon. But an agreement on the withdrawal has yet to be concluded.
''A visit to the area does not establish credibility,'' said a senior Egyptian official. ''Credibility equals an agreement on withdrawing all foreign forces from Lebanon.''
The official's remarks followed comments by other moderate Arab states. Saudi Arabia's state-run radio noted that Mr. Shultz was visiting the Middle East ''amid doubts about the desire of the United States to continue its peace efforts.''
Both American and Egyptian officials agree that a Lebanon troop withdrawal agreement is the first and badly needed cornerstone on which to rebuild US credibility shaken by: (1) the Lebanon impasse, (2) Israel's disregard of US protests about rapidly expanding Israeli settlement on the West Bank, and (3) the collapse of Jordanian King Hussein's efforts to find a way to join the Reagan peace plan with the acceptance of the Palestine Liberation Organization.
American and Egyptian officials hope that a pullout of all foreign forces from Lebanon would encourage PLO chief Yasser Arafat and King Hussein to resume their broken dialogue - and hence get the peace talks envisaged by the Reagan plan under way with the King and a Palestinian delegation joining in.
A meeting of the central council of Al Fatah - the largest Palestinian guerrilla organization - is reported to have ended in Tunis in the early morning hours Monday with a decision to reactivate the Jordanian-Palestinian talks. No communique was issued following the meeting but authoritative Palestinian sources say the Al Fatah central council ''approved Mr. Arafat's political line, in particular the resumption of negotiations with Jordan.''
Egyptian Foreign Minister Kamal Hassan Ali, in his welcoming remarks for Mr. Shultz at Cairo airport Monday, directed one of his comments at both the PLO and Jordan: ''The parties are called upon now more than ever to translate their genuine intentions into concrete actions in order to join the enlarged talks for the settlement.''
Egypt and the United States, however, appear to differ on the issue of a PLO role in future peace negotiations. In particular, Egyptian officials fear that the Israeli government of Prime Minister Menachem Begin may try to extract a promise from Mr. Shultz when he visits Israel that the PLO will be barred from all future peace negotiations in exchange for the withdrawal of Israeli troops from Lebanon.
Any such promise would be a ''far too high price,'' according to Egyptian officials.
Egyptian President Hosni Mubarak appears to have ruled out suggestions by both President Reagan and Mr. Shultz that the moderate Arab states should drop recognition of the PLO if Arafat does not endorse a negotiating role for King Hussein. Mr. Mubarak reiterated that Egypt upholds the 1974 Rabat Arab summit resolution recognizing the PLO as the ''sole legitimate representative of the Palestinian people.'' Saudi radio also said that President Reagan's suggestion made the chances for peace more remote and complicated the situation further.
Such differences, combined with doubts about President Reagan's political determination as the 1984 election approaches, suggest to observers that what Shultz called the ''quest for peace'' is likely to prove a daunting task for the secretary.
Egyptian Foreign Ministry sources were encouraged by at least one early sign: a Syrian Cabinet statement welcoming a visit to Damascus by Mr. Shultz.
Although Syria's official press predicted April 25 that Shultz would ''not breathe new life into the Reagan plan,'' sources close to Egypt's Foreign Ministry foresee a possible thawing of the ice between the United States and Syria.
The sources point to President Reagan's message to Syrian President Hafez Assad earlier this month stating that the United Nations Security Council Resolution 242, on which the Reagan plan and Camp David accords rest, applied not only to the West Bank and Gaza, but also to the Golan Heights.