"Time is running out for the people of Sudan," Annan wrote in an article published by the New York Times on Wednesday. "We need pledges immediately converted into cash, and more protection forces in Darfur to prevent yet more death and suffering."
"The billions pledged this week can help," he added. "But hungry people cannot eat pledges. Through long and bitter experience we've learned that donor pledges often remain unfulfilled."
Representatives of more than 60 countries and international organisations met in Oslo, Norway, on Monday to finance implementation of the Comprehensive Peace Agreement (CPA) - signed on 9 January by the Sudanese government and the Sudan People's Liberation Movement/Army (SPLM/A).
Annan warned that violence, disease and displacement remained daily realities in the "desperately impoverished region", where one in four children died before the age of five and nearly half of all children were malnourished.
"We know what we need: money to help win the peace in the south, more African Union boots on the ground to help end the atrocities in Darfur, and political pressure to settle the conflict. It's that simple, and that essential," Annan said.
At the two-day conference, donors demanded a swift resolution of the ongoing conflict in the western region of Darfur.
US Deputy Secretary of State Robert Zoellick told the conference on Tuesday: "If the government of Sudan and all those in Darfur fail to act to end the violence and to help strengthen security - then my country and others will not be able to sustain the CPA fully, and Sudan could slip back into the depths."
George Somerwill, deputy spokesperson for the UN Mission in Sudan, told IRIN on Wednesday: "There can be no long-term development in Sudan without peace in Darfur."
The Oslo conference was the first time that Sudan's government and the SPLM/A had presented themselves as one entity - through the recently established Joint National Transition Team (JNTT).
The JNTT presented a 6-year development plan to the conference, to correspond with the 6-year interim period of the CPA. The team had developed the plan in partnership with the World Bank, the UN and other donors.
According to a statement released by the UN Development Fund for Women (UNIFEM) on Wednesday, women from north and south Sudan urged donors to reflect strong gender-responsive principles in the allocation of resources.
UNIFEM’s executive director, Noeleen Heyzer, told the conference that women were central to the enormous tasks ahead and could accelerate the building of peace, security and prosperity.
"They are not just victims; they are also part of the solution," she said.
A day before the conference started, UNIFEM, the Norwegian Ministry of Foreign Affairs and the Norwegian Institute of International Affairs convened a gender symposium in Oslo, which brought together more than 50 Sudanese women to agree a common agenda.
Norway’s minister for international development, Hilde F. Johnson, told the symposium: "The women of Sudan must be central to the peace process."
Meanwhile Amnesty International (AI) - in a statement released on Monday - called on donors to set clear benchmarks for everything they offered to Sudan.
"The government continues to breach its human-rights obligations contained in the [CPA] - which guarantees the right to life, the right not to be tortured and the right not to be arbitrarily arrested," Benedicte Goderiaux, AI's Sudan researcher, said.
The SPLM/A also had a poor record of accountability in southern Sudan, the statement added, noting that expenditure programmes in the past had often perpetuated discrimination.
AI recommended that donors fund an independent human-rights commission for Sudan, as well as commissions for gender and equality, comprehensive restructuring of the security services and strong justice and accountability mechanisms, in order to address the discrimination and injustice AI said had fuelled wars in the country.