Abul Gheit, the Egyptian foreign minister, said Mufid Shehab, the legal and parliamentary affairs minister, would represent the country.
Mubarak's decision to stay away indicated the failure of intense mediation efforts undertaken by Saudi Arabia and Libya with the aim of ensuring he attended, sources told Al Jazeera.
"The decision proves that the oustanding issues between Egypt and Qatar have yet to be resolved," Lamis Andoni, Al Jazeera's analyst, said.
One of the leaders expected to attend the summit is Omar al-Bashir, the Sudanese president, who is facing an arrest warrant from the International Criminal Court for alleged war crimes and crimes against humanity in his country's western Darfur province.
Ziad Haidar, a Syrian journalist, told Al Jazeera that Syria and Egypt regard the arrest warrant as a "political and not a legal issue".
He said that if the two countries can persuade Russia and China, their UN Security Council member allies, to prevail on the ICC to postpone the arrest warrant "at least for a year", they could buy time for mediation to resolve the Darfur issue.
In his opening address, Amr Moussa, secretary-general of the Arab League, expressed hope that Qatar would continue mediating talks on Darfur until a breakthrough is achieved.
For his part, Hamad bin Jasim al-Thani, Qatar's prime minister, said "the challenges are numerous and threats are many, and the Arab people are looking to us to see if our words will be coupled with actions".
Israel and Iran
Prospects for peace in the Middle East could be complicated by the pending return to power in Israel of Benyamin Netanyahu, whose Likud party rejects the creation of an independent Palestinian state and takes a hard line on security issues.
While acknowledging the urgency of Gaza's reconstruction, Arab governments led by Saudi Arabia are wary of growing Iranian influence in the region, and especially Tehran's support for the Palestinian territory's Hamas rulers and Lebanon's Hezbollah group.
|Iran's nuclear programme has been a cause for concern among some Gulf Arab states [AFP]
At issue is Tehran's nuclear programme, which Tehran insists is for generating electricity.
But many Arab states share the suspicion of Western powers that Iran is trying to build an atomic bomb under a civilian cover.
"As much as we appreciate Iran's support for Arab causes, we would like to see it channelled through Arab legality and be in harmony with its objectives," Saud al-Faisal, the Saudi foreign minister, said this month.
The Doha summit follows a recent meeting by Abdullah bin Abdulaziz Al Saud, the Saudi king, with the presidents of Egypt and Syria.
The conference, which sought to promote reconciliation, allowed Egypt and Saudi Arabia to improve contacts with Syria - a major ally of Iran - which had worsened during the war on Gaza.
Cairo and Riyadh are staunch supporters of Mahmud Abbas, the Palestininian president, while Damascus and Doha back Hamas, which routed Abbas's Fatah loyalists from Gaza in factional fighting in June 2007.
Egypt has been brokering reconciliation talks between Fatah and Hamas, and they are due to resume negotiations on April 1 after failing in a first round to agree on the composition of a unity government.
Abdullah warned last week that "the Palestinian dispute ... is more serious in jeopardising our just cause than Israeli aggression".
Confirming the issue's significance, Ahmed bin Helli, the Arab League deputy chief, told the AFP news agency: "Inter-Arab reconciliation figures high on the summit's agenda."
A Qatari official expressed hope that the Doha gathering will "serve to streamline Arab relations and relaunch a common Arab action that has a firm basis".