Sudan's government and southern rebels committed themselves on Friday to ending Africa’s longest civil war by December 31, signing a pledge in front of 15 UN Security Council ambassadors.After the signing ceremony, the Security Council — meeting away from its New York home for the first time in 14 years — unanimously adopted a resolution promising political and substantial economic support once Sudan ended two wars that have left millions dead in the south and in Darfur in the west.With the Council’s ambassadors as witnesses, the Sudanese government and the Sudan People’s Liberation Movement (SPLM) signed a document declaring ‘‘their commitment’’ to complete a final accord by December 31 and end 21 years of war. Sudanese Vice President Ali Osman Taha and southern rebel leader John Garang, the main peace negotiators for the two sides, have made similar, failed pledges over the past year. US ambassador John Danforth, the current Council president, acknowledged some believed the Council had come to Kenya to deliver ‘‘grand words’’ while people were dying. ‘‘It’s up to you to prove the naysayers and sceptics wrong,’’ he told Taha and Garang at the meeting. ‘‘The violence and atrocities being perpetrated must end now. You have heard this message clearly from the Security Council — heed it.’’But human rights and humanitarian groups were not convinced, with Amnesty International calling for a mandatory arms embargo on all parties. ‘‘From New York to Nairobi, a trail of weak resolutions on Darfur has led nowhere,’’ said Caroline Nursey, regional director of the Oxfam charity. Jerema Rome of Human Rights Watch feared Sudan ‘‘will take this resolution as a blank cheque to continue its persecution of the civilian population in Darfur’’.The Council’s resolution said it would consider ‘‘appropriate’’ actions if Sudan did not follow through on its commitments. It asks the UN, the World Bank and others to devise a reconstruction plan, including possible debt relief, for Sudan once there is peace. —Reuters