The U.S.-Israeli war on Iran has caused a surge in energy and fertilizer prices and could push more than 30 million people into poverty, the head of the U.N. Development Program said Wednesday.

"It's development in reverse," Alexander De Croo told AFP on the sidelines of a G7 development meeting in Paris.

"It took decades to build stable societies, to develop local economies, and it took only several weeks of war to destroy that," he added.

"We did a study after six weeks of war and estimated that even if the conflict ended at that point, 32 million people would be pushed into precarity in 160 countries," said De Croo.

The war has led to closure of the Strait of Hormuz, through which a fifth of the world's oil and liquefied natural gas flows in peacetime.