Sudan's President Omar al-Bashir has said in a letter to the UN he backs plans for a join UN-African Union force in the troubled region of Darfur.
Mr Bashir has remained opposed to a large UN force
In the letter to the secretary general, Mr Bashir says he wants to begin "immediately" to implement UN plans.
However, diplomats note that Mr Bashir remains opposed to any large-scale UN deployment and has gone back on agreements on Darfur before.
More than 200,000 people have died in the three-year conflict in Darfur.
The UN envoy to Khartoum, Ahmedou Ould Abdallah, is expected to brief a Security Council meeting on Darfur on Wednesday afternoon.
The main thrust of the three-part UN plan for Darfur is to strengthen the current 7,000-strong African Union force with UN troops.
Mr Bashir has remained consistently opposed to any large UN deployment but now appears to have agreed to the strengthening of a hybrid force.
Mr Bashir says Sudan agrees to the first two parts of the UN plan - deployment of new staff and equipment to the African Union force followed by a larger support package.
However, the third part of the UN plan - the size and command of the new force - is not finalised in the letter.
And UN diplomats expressed fears that carrying out plans through a special panel - the Tripartite Committee of Sudan, the UN and the AU - would give Khartoum an effective veto.
Sudan's change of heart on its previous opposition to UN participation follows international threats of trade sanctions and of a ban on aircraft movements over Darfur, to stop bombing raids by government forces.
The Darfur conflict began in 2003 after a rebel group began attacking government targets, saying the region was being neglected by Khartoum.
The rebels say the government is oppressing black Africans in favour of Arabs.
Arab militias responded to try to put down the uprising. The government denies accusations from the rebels it is backing the militias.