The monarch of Morocco decided against attending the summit over what the kindgdom called neighbouring Algeria's "surprising official positions" on Western Sahara that have hurt Moroccan interests.
"The summit is postponed to give more time to solve the dispute and hold the next summit without problems," Mauritanian Foreign Minister Mohamed Vall Ould Bellal told Aljazeera on Monday.
Maghreb delegates confirmed the Tripoli summit had been postponed.
Libyan Foreign Minister Mohammed Abdel-Rahman Shalgam had earlier said the summit would be held on 25-26 May.
Libya declined to comment.
Reporting from Tripoli, Aljazeera's Khalid al-Dib said earlier that the optimism demonstrated by the summit organisers was not in tune with ground realities.
The Moroccan Foreign Ministry confirmed reports that the king would not attend the first gathering since 1994 of heads of state of the five Maghreb nations.
The king was to be represented in Tripoli by Foreign Minister Mohamed Benaissa, government officials, speaking on the condition of anonymity, said.
Bouteflika's recent remarks on
Western Sahara irked Morocco
"Algeria has taken the responsibility of compromising an opportunity to relaunch ... (North African) construction," the ministry statement said.
The Foreign Ministry said statements by Algerian President Abdelaziz Bouteflika supporting independence for Western Sahara "directly affect the higher interests of the (Moroccan) kingdom".
Libyan leader Muammar al-Qadhafi organised the summit in hopes of relaunching the Union for an Arab Maghreb, which has never got off the ground, largely because of tensions between Morocco and Algeria over Western Sahara.
Morocco's Information Minister Nabil bin Abdullah, speaking to Aljazeera from Rabat, hoped North African leaders would resolve their differences and propose practical plans to reactiviate the union.
"The summit is a positive development, so we hope that this summit will contribute to building the Arab Maghreb Union," bin Abdullah said.
"It is regrettable that Algeria is still persisting with its approach by going in the opposite direction of Moroccan interests"
Nabil bin Abdullah,
Moroccan Information Minister
But he blamed Algeria for not cooperating to solve the difference on the Western Sahara.
"It is regrettable that Algeria is still persisting with its approach by going in the opposite direction of Moroccan interests," bin Abdullah said.
Algeria's support for the Polisario had cast a dark shadow on the summit, al-Dib said.
On the other hand, Hasan Araibi, a member of the Algerian parliament, defended Bouteflika's stand and said his intention was to strengthen international legitimacy.
"Morocco has acknowledged that the Sahrawi issue is a problem," Araibi told Aljazeera.
Welfare in unity
"We Algerians are working on complete normalisation of Algerian-Moroccan relations," Araibi said. "However, the Arab Maghreb's welfare lies in its unity and in resolving all disagreements as the whole Arab nation."
"If the Sahrawi people are given the chance to decide and they choose Morocco, we would then congratulate our Moroccan brothers," he added.
Mineral-rich Western Sahara was
annexed by Morocco in 1975
Morocco annexed in 1975 the vast mineral-rich territory colonised by Spain. The following year, Polisario Front rebels based in camps in southern Algeria began a desert war against Morocco to gain the territory's independence.
Years of UN efforts to organise a referendum on self-determination have been fruitless, in large part because Morocco and the Polisario failed to agree on who could be counted as voters.
Morocco has proposed a political solution to the Western Saharan conflict providing for autonomy.
Polisario leader Mohamed Abdelaziz was quoted over the weekend as saying that the rebels could decide to rearm themselves.
Abdelaziz told a news conference last week that a ceasefire in effect since 1991 and surveyed by the UN was called so that the referendum could be organised.
The region's residents "could take up arms again if such an objective is not reached", Abdelaziz was quoted as saying by the Polisario news agency.
The region's residents "could take up arms again if such an objective is not reached"
The Polisario leader also saluted Algeria's "constant position in support of the Sahrawi people's legitimate right to self-determination".
The Algerian president sent a message spelling out his country's support "in favour of people colonised or under foreign occupation".
Last month, the UN Security Council extended the UN's mission to the Western Sahara for another six months, until the end of October and called on the Polisario to free Moroccan prisoners it has held for years.