(CNN)More than half of the world's children are at risk one or more of three threats -- conflict, poverty and discrimination against girls -- according to a new report from Save the Children.
Half of world's children at risk of war, poverty, discrimination, report finds
The report, published ahead of International Children's Day on June 1, estimates 1.2 billion children are exposed to at least one of those risks. Of those, 153 million children are at extreme risk of all three.
"More than half the world's children start their lives held back because they are a girl, because they are poor or because they are growing up in a warzone," the report said.
"Early marriage, child labor and malnutrition are just some of the life-changing events that can rob children of their childhood."
The organization's second annual End of Childhood Index ranked countries on how much children in each country face death, malnutrition, lack of education and being forced into marriage, motherhood or work.
"Despite their economic, military, and technological might, the United States (36th), Russia (37th) and China (40th) all trail Western European countries in the index," said the report.
Singapore and Slovenia tied for top place in the ranking, while Niger ranks last among countries surveyed.
Almost all developed countries have little or no change in their scores, according to the report, with 25 of 30 countries moving two or fewer points in either direction.
Australia (16th) improved its ranking, while Germany (12th) and the UK (12th) maintained their positions.
The world's poorest children are concentrated in rural areas (81%). Most live in sub-Saharan Africa (52%) and South Asia (36%). India alone is home to 30%, said the report.
"Overall, the data collected for the End of Childhood Index document tremendous gaps between rich and poor countries and the urgent need to accelerate progress for the most vulnerable children," said the report.
High-income countries also have large equity gaps in child survival, the report added.
"In the United States and Canada, infants from indigenous communities die at higher rates -- 40% higher than the national average in the US and 20 to 360% higher than the rest of Canada," it said.
The report said that although in most regions, child mortality rates have declined substantially faster for the poorest than for the richest households since 2000, they are not closing fast enough.
For example, the global number of child laborers has declined by close to 40% since 2000, but an estimated 152 million children are still trapped in child labor, compelled to work to support themselves and their families.
The report also found that more than one billion children live in countries plagued by poverty; 240 million in countries affected by conflict and fragility; and more than 575 million girls live in countries where gender bias is a serious issue.
"Closing gaps between rich and poor would save millions of young lives," the report concluded.