The United Nations Security Council is likely to vote on Thursday on a British-drafted resolution that demands a halt to the siege of al-Fashir in Sudan's North Dafur region by the paramilitary Rapid Support Forces (RSF), diplomats said on Wednesday.

The draft text, seen by Reuters, also calls for an immediate halt to the fighting and for de-escalation in and around the city and the withdrawal of all fighters that threaten the safety and security of civilians.

Britain has asked for the draft to be voted on by the 15-member council on Thursday afternoon. A resolution needs at least nine votes in favour and no vetoes by Russia, China, the United States, Britain or France to be adopted.

War erupted in Sudan in April last year between the Sudanese army (SAF) and the Rapid Support Forces (RSF), creating the world's largest displacement crisis.

Al-Fashir is the last major city in the vast, western Darfur region not under control of the RSF. The RSF and its allies swept through four other Darfur state capitals last year and were blamed for a campaign of ethnically driven killings against non-Arab groups and other abuses in West Darfur.

Top UN officials warned the Security Council in April that some 800 000 people in al-Fashir were in "extreme and immediate danger" as worsening violence advances and threatens to "unleash bloody intercommunal strife throughout Darfur."

The draft Security Council resolution "demands that all parties to the conflict ensure the protection of civilians, including by allowing civilians wishing to move within and out of Al-Fashir to safer areas to do so."

It also calls on countries "to refrain from external interference which seeks to foment conflict and instability and instead to support efforts for a durable peace and reminds all parties to the conflict and member states who facilitate the transfers of arms and military material to Darfur of their obligations to comply with the arms embargo measures."

The US says the warring parties have committed war crimes and the RSF and allied militias have also committed crimes against humanity and ethnic cleansing. The UN says that nearly 25-million people - half Sudan's population - need aid and some eight million have fled their homes and hunger is rising.

Between 10 000 and 15 000 people were killed in one city alone in Sudan's West Darfur region last year in ethnic violence by the RSF and allied Arab militia, according to a UN sanctions monitors report, seen by Reuters in January.

The draft text to be voted on by the Security Council "calls on the parties to the conflict to seek an immediate cessation of hostilities, leading to a sustainable resolution to the conflict, through dialogue."