Qatar paid $2.3m out of the $7m it promised, sources at the Arab League said on Tuesday. The pan-Arab body made a total pledge of $150m during its latest summit in Khartoum last March.
The 7,000-strong cash-strapped and ill-equipped African Union (AU) force has failed to stem the bloodshed in Darfur, where up to 300,000 people have died since the start of a civil war in February 2003.
The conflict pits local rebels, who complain that Khartoum ignores the needs of the area and discriminates against them, against government forces and Khartoum's allied Arab militia.
Known as the Janjaweed, the militia has been blamed for mass murder, rape, and the burning of villages, causing thousands more to flee the area - many of them going in to neighbouring Chad. Sudanese government has strenuously dismissed the allegations.
The AU's Peace and Security Council is due to gather in New York on Wednesday to decide whether or not to extend its mandate beyond its official expiry on September 30.
The African body, whose Darfur deployment was its first peacekeeping mission, has already asked the UN to take over but its request has been roundly rejected by Khartoum.
Late last month, the Security Council adopted a resolution calling for the deployment in Darfur of up to 20,000 peacekeepers, a plan which Omar al-Bashir, Sudan's president, has fiercely opposed and branded as a US-engineered attempt to overthrow his government and plunder his country.
The Arab League has supported Sudan in rejecting the deployment of western troops in Darfur and called for further dialogue between Khartoum and the UN on the issue.