Arab leaders opposed to Egyptian President Anwar Sadat 's go-it-alone diplomacy were reportedly near success early this morning in their efforts to form a common front to forestall a separate Egyptian-Israeli peace.

The summit conference of five countries two Palestinian groups, deadlocked for three days because of leadership rivalries and policy differences, is expected to produce only a limited cooperation and a minimum joint program against Sadat, however,

Reports leaking out of the closed door meeting, which began at 7 p.m. last night and continued after midnight, indicated that the leaders were determined the embarrassment of a public of disarray.

Even after the evening session had begun, however, Iraqi sources expressed their continued disappointment with the positions taken by the other parties, and observers suggested that a last- minute breakdown in the conference could not be ruled out.

Leaders of Algeria Iraq. Libya, South Yemen and Syria and the Palestinian organizations ahve been meeting here since Thursday in an effort to agree on a program for countering the effects of Sadat's trip to Israel last month and planned Cairo talks that will bring Israeli. Egyptia, U.S. and U.N. officials together later this month.

Although Iraq's reason for displeasure were not spelled oit, observers suggested that Iraq, the most militant of the countries meeting here, had failed to win support for its policy demands.

At the center of the argument was Syrian President Hafez Assad's reluctance to give in to traditional rival Iraq on the key question of leadership of the anti-Sadat camp.

Traq is reported pressing Syria to repudiate its stand adopted after the 1973 Arab-Israel: war when it accepted the principle of negotiations for a Middle East settlement.

Iraq has also called for a follow up anti-Sadat summit meeting in Baghdad. A major issue of any agreement here, observers said is whether it sets a date for such a meeting.

Iraq originally sought to sabotage the Tripoli meeting by proposing the rival summit in Baghdad. Only at the last minute did Iraq agree to come here.

If Assad agrees to go to Baghdad, the Iraqis can be expected to claim that his presence there symbolizes a a public admission of his errors in the long and violent dispute between the nations ruled by rival branches of the Baath Socialist Party.

If no Baghdad meeting is set, Iraq will have been rebuffed.

The while scope of the anti-Sadat front could he brought into question without a public show of reconciliation - no matter how fragile it may prove to be in the light of a similar short-lived agreements in the past.

Informed sources reported that all parties except Iraq had agreed to concessions after the first two days of formal and talks failed to break the deadlock.

In another development indicating the state of flux in Middle East developments, King Hassan 11 of Morocco canceled plans to visit Washington Wednesday and Thursday, President Carter met for an hour yesterday with Morocco Prime Minister Ahmed Osman, who make a special trip to Washington to inform the administration of the cancellation.