By Barnaby Mason
BBC Diplomatic Correspondent
The signing of an agreement between the Sudan Government and southern rebels on the sharing of oil revenues between north and south is the latest significant step towards an overall settlement of the civil war.
The US is putting pressure on both sides to end the war
The United States and other western countries have played a crucial part in the peace process that began in Kenya in early 2002.
Special envoys from the United States, Britain, Italy and Norway have been active behind the scenes alongside African mediators at the marathon Sudan peace talks.
It is American pressure that counts most: a public signal of it came in October when the Secretary of State, Colin Powell, went to meet both sides in Kenya.
Oil and terror
The key incentives held out to the government in Khartoum are the lifting of American sanctions and the dropping of Sudan from Washington's list of states it regards as sponsors of terrorism.
The Bush administration has an interest in making sure that Sudan is not a refuge for al-Qaeda or similar organisations; after all, Osama bin Laden lived in Khartoum in the early 1990s when militant Islamists were dominant in northern Sudan.
Another big reason for American interest is Sudan's recently developed oil wealth - the subject of the agreement.
The Bush administration is always looking for new sources of supply and has declared African oil to be a strategic national interest.
Much of Sudan's oil lies in the south and existing fields straddle the north-south divide, so full exploitation by western companies means an end to the war and a stable government.