"The way forward is a durable ceasefire, open crossings and Palestinian reconciliation under president [Mahmoud] Abbas. Efforts to achieve this need your united support."
Ban also expressed concern over Sudan's suspension of international NGO activity in its western region of Darfur, a move that came after the International Criminal Court (ICC) issued its arrest warrant for al-Bashir on charges of war crimes.
Al-Bashir, who attended the conference despite the warrant, defended himself in his speech and also urged support for the Palestinians.
He also hit out at the UN security council, the body that mandated the ICC prosecutor to investigate the situation in Darfur, accusing the West of having launched a "media coup" against the Sudanese government.
Qatar is not a signatory to the ICC and therefore not obliged to arrest al-Bashir.
"He touched on all the issues that are important to the Arab world," Al Jazeera's Sami Zeidan, reporting from the summit venue, said.
While seventeen heads of state are attending the two-day gathering, more than initially expected, there have been some notable abstentions.
Hosni Mubarak, the Egyptian president, has not shown up for the conference, sending instead a low-level delegation, widely seen as a snub to Qatar.
|Delegates gathered in Doha for the Arab League's 21st summit
Meanwhile, shortly after the opening session began, Libya's Muammar Ghaddafi attempted to address Saudi Arabia's monarch but was stopped for speaking out of turn.
He walked out, but reportedly returned to the conference later.
Divisions among Arab leaders are largely over responses to Israel's 22-day onslaught against the Hamas-ruled Gaza Strip at the beginning of the year and the growing regional influence of Iran.
Bashar al-Assad, the Syrian president, who is handing over the presidency of the Arab League to Qatar, opened the summit with a speech calling for unity among Arab states.
He also used the opportunity to hit out at Israel, saying "there is no peace partner for Arabs in Israel".
Sheikh Hamad bin Khalifa Al Thani, the emir of Qatar who is hosting the conference, spoke second, mainly on the financial crisis.