The U.N. chief criticized Sudan Monday for expelling aid agencies in Darfur at an Arab summit attended by the defiant Sudanese president, who dismissed international war crimes charges against him.

The tough exchange at the opening of an Arab League summit was the first direct encounter between Sudanese President Omar al-Bashir and U.N. Secretary-General Ban Ki-Moon since the International Criminal Court issued an arrest order for al-Bashir earlier this month on the war crimes charges.

The encounter highlighted the vast divide over al-Bashir — with fellow Arab leaders rallying behind him, and the backers of the court left widely powerless to bring him to justice as long as he remains in friendly territory.

"Relief efforts should not become politicized," Ban said in a speech to the summit attended by al-Bashir. "People in need must be helped irrespective of political differences," he added in an appeal to resume relief efforts to Darfur.

Al-Bashir attacked the U.N. Security Council — which asked the international court to open the Darfur war crimes investigation. He called it an "undemocratic institution that ... applies double standards, targeted the weak and gave a blind eye to the (real) criminals."

He claimed the United Nations cannot keep its credibility "with some countries having hegemony."

Al-Bashir had a receptive audience.

He arrived Sunday in Qatar — embraced by the tiny Gulf nation's emir at a lavish airport ceremony. Earlier this month, the Arab League made clear it would not arrest al-Bashir if he attended the summit, saying that would only enflame the conflict between the Arab-led government in Sudan and ethnic Arab rebels in Darfur.

The United Nations estimates that the fighting has killed up to 300,000 people and driven 2.7 million from their homes since 2003.

Only Jordan and two other tiny Arab League members, the Comoros and Djibouti, are parties to the ICC charter, but they can take no action on Qatari soil. Arab foreign ministers have endorsed a draft resolution for the summit rejecting the ICC's arrest warrant issued on March 4.