Kofi Annan has said the United Nations should not be blamed for the world's inaction in Sudan's Darfur conflict.
Food is running short for Darfur's refugees
The UN chief was in charge of peacekeeping during the 1994 genocide in Rwanda and was widely criticised.
Some human rights campaigners say a genocide is being carried out against black Africans in Darfur by Arab militias but Mr Annan disagrees.
Some one million people have fled what the UN calls "a campaign of ethnic cleansing" in Darfur.
"We should avoid the situations where we allow member states to hide behind the secretary general, use him as an alibi for their own inaction," Mr Annan said.
In April, Mr Annan drew comparisons with the Darfur conflict during a speech to mark the 10th anniversary of the Rwandan genocide.
Talks between the government and Darfur rebels are due to begin in Paris this week.
The Darfur conflict has been described as the worst humanitarian situation in the world by the UN.
In Darfur, aid agency Medecins Sans Frontieres says that the Arab "Janjaweed" militia is still operating, despite government promises to disarm them.
MSF says that some 80,000 people who have fled their homes are "virtually imprisoned" in the town of Mornay.
Men who venture outside the town are killed and women raped, MSF says.
Talks are aimed at ending a conflict that has displaced a million people
The government and the two main rebel groups - the Sudan Liberation Movement and the Justice and Equality Movement - signed a ceasefire in April, but each side has accused the other of violating it.
There has been strong criticism of Sudan for failing to curb the Janjaweed militia.
At the end of May the government signed a separate peace deal with southern rebels, bringing hope of the end of a conflict that has divided the country since 1983, killing two million people.