MILAN (AP) — Former U.N. Secretary-General Kofi Annan and Mozambican humanitarian Graca Machel are addressing a summit on the crisis of malnutrition, which is an underlying cause for half of the child deaths worldwide.

Organizers on Saturday announced $640 million in new commitments to tackle global malnutrition, bringing pledges over the next decade to $3.4 billion. That still falls far short of the $3.7 billion a year the World Bank says is needed to make progress on issues like stunted growth or anemia in women.

Machel, the widow of Nelson Mandela, says one of the challenges in the campaign is that malnutrition "is a hidden pandemic. It is not visible in daily life."

Some 155 million children globally suffer stunted growth due to malnutrition, which hurts their physical and cognitive development.