Foreign ministers meeting in Tripoli on Monday sought to play down a new row between Morocco and Algeria over Western Sahara and said the issue would not be discussed in Tripoli.
Morocco has reacted angrily to President Abdelaziz Bouteflika's reiteration of Algeria's support for the Polisario and its independence struggle on Saturday.
Diplomats and experts say ignoring Western Sahara will harm regional integration.
The meeting scheduled for 25-26 May has been put off to 26-27 May following the death of the elder brother of the Tunisian President Zine El Abidine Ben Ali, Aljazeera learned.
The leaders of a region of 80 million inhabitants meet in the Libyan capital to breathe new life into a once-hyped project to form a regional trade bloc, as well as boosting security, immigration and political cooperation.
"After 11 years we have now succeeded in organising a summit," Libyan Foreign Minister Mohammed Abdel-Rahman Shalgam told reporters as ministers met to prepare for the summit.
The Arab Maghreb Union (AMU) was set up in 1989 to create a free trade zone to mirror the European Union across the Mediterranean and promise greater social and political integration.
Algeria, Morocco, Mauritania, Libya and Tunisia have held only one summit since then, largely because of rivalries between Rabat and Algiers over Western Sahara.