The appearance of Sudan's President Omar Hassan al-Bashir, flouting an international arrest warrant, is set to overshadow efforts to heal a deep Arab rift over how to handle rising power Iran, reported Reuters.
Bashir flew into the small Gulf Arab state on Sunday after visits to Egypt, Eritrea and Libya in the weeks since the International Criminal Court (ICC) indicted him on charges of masterminding war crimes in Darfur.
Arab states have given strong backing to Sudan.
After the demise of Saddam Hussein, international justice for Sudan's leader would set another troubling precedent for Arab leaders accused by rights groups of ruling by repression.
Qatar, which hosts a key U.S. military base, said last week it had faced unspecified pressure not to receive Bashir but it repeated an invitation for him to attend.
Bashir's presence poses a challenge for the summit of the 22-member Arab League but officials in Doha said Saudi Arabia had pressed the summit to offer strong support for Sudan.
Bashir adviser Mustafa Osman Ismail told reporters in Doha: "We expect this popular uprising of support for Sudan, not just in the Arab world, to be translated into a strong resolution that meets the hopes of the Arab street."
Qatar, now a major natural gas power, has billed the summit as a chance for reconciliation among Arab states over a series of regional conflicts linked to non-Arab Shi'ite power Iran.
Arab governments have struggled to respond to Iran's political clout since the U.S. invasion of Iraq in 2003 brought long-oppressed Shi'ite Muslims to power there.
But Qatar, with ambitions to be a major regional powerbroker, has maintained close links with Iran, despite U.S. and Arab pressure to keep its distance from a country they suspect of seeking to develop nuclear weapons.
The Egyptian and Saudi leaders see Iran's hand behind the strength of Hezbollah in Lebanon and Hamas in the Palestinian territories -- Islamist groups that refuse to renounce armed action in the historic Arab conflict with Israel.
Egypt's President Hosni Mubarak is not expected to attend because of lingering rancor over Qatar's attempts to rally Arab countries and Iran behind Hamas during Israel's war on Gaza, which is under the control of Hamas.
But Saudi Arabia's King Abdullah, attending despite Saudi misgivings over Qatari policy, has reconciliation as a priority.
Riyadh, which sees itself as the bastion of mainstream Sunni Islam, fears Washington will end its conflict with Iran at the expense of its traditional oil-for-security ally.
"The Doha summit is still a battleground between the emerging de facto alliance between Qatar, Syria and Iran on one side, and the Saudis, Egyptians and Jordanians on the other," said Ali al-Ahmed, a U.S.-based Saudi dissident.
But he added: "Bashir will certainly steal the limelight and give a roaring speech."