The comments come after US President Donald Trump this month proposed to cut Washington's contribution to UN peacekeeping operations -- the largest share of funding for the organization's missions -- to 25 percent of their total budget, compared to just under 30 percent today.
"We are doing our utmost to spend as little as possible" and "modernize," Herve Ladsous, the outgoing head of peacekeeping operations, said during his final news conference after six years in his post.
"Sixteen missions and 120,000 men deployed around the world for 0.4 percent of the world's military expenditure, it's still very little," Ladsous said.
"We have always tried to reformat missions, whenever possible, to be as economical as possible," he added.
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"We review mandates, staffing and equipment on a regular basis," he said, pointing to the closure of missions to Ivory Coast, Liberia and Haiti, which would result in "hundreds of millions of dollars in savings."
Ladsous also criticized what he called a lack of support from members of the UN Security Council who he said are sometimes too lenient toward governments that obstruct the work of peacekeeping missions, including South Sudan's.
He had recommended an arms embargo against Africa's newest country, a measure supported by Britain, France and the United States but rejected by the Security Council in December thanks to opposition by China and Russia.
The Security Council should also continue the UN's mission in the Democratic Republic of the Congo, its largest -- at 19,000 troops -- and one of its oldest, Ladsous said. Maintaining the operation at the current force is necessary because of electoral turmoil in the country, he added.
Trump's plan for severe cuts to US funding has alarmed the United Nations, along with US allies and international NGOs. US military officials and diplomats also worry the cuts will reduce Washington's ability to play a leading role in the world.