U.N. Secretary General Ban Ki-moon here Monday criticized the Sudanese government for expelling international aid groups from Darfur in the wake of the International Criminal Court's (ICC's) issue of a arrest warrant for Sudanese President Omar al-Bashir. "I urge the Sudanese authorities once again to reverse this decision," he said in an address to the opening ceremony of the 21st Arab League summit, Xinhua reported. Sudan expelled 13 NGOs in response to the ICC issue of the arrest warrant for Bashir on March 4 for alleged war crimes in Darfur. Ban said he is "extremely concerned" about Sudan's decision to expel international aid groups from Sudan which supply life-sustaining services in the country. Bashir is also attending the summit. This is the first time for the two to sit together after the ICC issued the arrest warrant for Bashir. Ban said the international community must work together to transcend the tensions related to the ICC. "Relief efforts should not become politicized," he said. People in need must be helped irrespective of political differences, Ban said.