With more than a billion people still struggling to survive on less than a dollar a day, U.N. Secretary-General Kofi Annan (search) urged leaders of the major industrialized nations Thursday to double their aid to developing countries and keep promises to drop trade barriers.

In an open letter to the leaders who will be meeting in France starting Sunday, Annan said it was time for the eight most powerful countries "to set aside recent differences" over the war in Iraq "and give due priority to the issues of poverty and development."

He called on the Group of Eight (search) countries to keep the pledge they made for the first time at the start of a new round of global trade negotiations in Doha, Qatar, in 2001 to treat the needs and interests of developing countries as a priority.

The pledge included taking up agricultural subsidies and tariffs that put developing countries at a disadvantage and an agreement to make sure poor countries could afford medicines to treat diseases like HIV/AIDS and tuberculosis.

Since then negotiations have bogged down and Annan said there was concern a September ministerial meeting of the World Trade Organization in Cancun, Mexico, "will pass without those two vital promises being met."

He urged leaders of the eight nations -- the United States, Japan, Russia, France, Britain, Germany, Italy and Canada -- to "summon the political will" so the hopes of millions in the developing world aren't dashed and developing countries maintain their belief in an open market system that gives everyone a fair chance.

Annan, who has been invited to Sunday's meeting with the G-8 (search) leaders, also urged them to tackle three crises in Africa at the same time because each feeds on the other: hunger, the HIV/AIDS epidemic, and the "emaciated capacity" of many countries to govern.

The world also needs to double its spending on water infrastructure to try to meet the U.N. goals of cutting in half the number of people without access to safe drinking water and sanitation by 2015, he said.