Speaking ahead of a meeting with the European Union Troika in Luxembourg, Del Ponte said her report on Serbia's cooperation with the UN court would be negative.
In May, the EU suspended negotiations on a Stabilisation and Association Agreement with Serbia over insufficient cooperation with the Hague tribunal. The European Commission set full cooperation that would lead to Mladic's arrest and extradition as a condition for the resumption of the negotiations.
In the meantime, the Serbian government adopted an action plan to achieve full cooperation, but Del Ponte said the plan had yielded no results so far.
After meeting Del Ponte, the EU Troika will meet a Serbian delegation led by Prime Minister Vojislav Kostunica.