He said over the last two years, there had been huge progress on the humanitarian front in Darfur that was now in danger of being swept away by renewed violence from all sides, increased obstructionism from the Sudanese government and a dwindling of funding from donors.

    "Humanitarian aid is vital for saving lives, but aid alone is a fatally insufficient response to the world's killing fields. Humanitarianism should never be used as a fig leaf for political inaction. And yet this is precisely what is happening today in Darfur," he said.

    "In 2004, we had only 230 relief workers on the ground to assist 350,000 people. Today we help ten times that number -- half of Darfur's population," he wrote.

    He said work together, UN agencies and NGOs have reduced deaths among those displaced in Darfur by two-thirds from their 2004 levels while halving malnutrition rates in 2005.

    "Unarmed relief workers can keep people alive today, but they cannot prevent them from being murdered, raped or forced from their homes tomorrow," he said.

    Peace talks have dragged on in Abuja while violence has escalated in Darfur to the point that aid workers cannot reach thousands of refugees.

    The aid workers said a deal is vital before the rainy season begins in June when planting of food crops must be completed.

    The three-year conflict between Darfur's rebels, mainly ethnic African farming tribes, and the Arab-dominated central government has killed about 180,000 people, mostly through disease and hunger.

    Decades of low-level tribal clashes over land and water in Darfur erupted into large-scale violence in early 2003 with rebels demanding regional autonomy. Enditem