The UN children's agency says one billion children around the world are still deprived of food, shelter, clean water and healthcare 20 years after the adoption of a treaty guaranteeing children's rights.
Hundreds of millions more children are constantly threatened by violence, Unicef said in a report released on Thursday assessing the situation two decades after the UN adopted the Convention of the Rights of the Child on November 20 1989.
The treaty has since been ratified by all countries except the US and Somalia, and more than 70 countries have used the treaty to incorporate children's rights into their national laws.
While saying Unicef had chalked up a "remarkable achievement" in recording a sharp decline in child deaths and getting an increasing number of children to attend primary school, Ann Veneman, the agency's executive director, urged the world to do more.
"As the first decade of the 21st century comes to a close, the convention stands at a pivotal moment," she told a news conference launching the report at the UN headquarters in New York on Thursday.
"Its relevance remains timeless. The challenge for the next 20 years is to build on the progress achieved, working together to reach those children who are still being denied their rights to survival, development, protection and participation."
Veneman said it was unacceptable that more than 24,000 children under the age of five die every day from preventable causes such as pneumonia, malaria, measles and malnutrition.
About 200 million children are chronically malnourished, more than 140 million are forced to work, and millions of girls and boys of all ages are subjected to sexual violence, the report says.
Violence
It also estimates that up to 1.5 billion children experience violence annually.
Veneman said there was a new focus on safeguarding the young "from violence, abuse, discrimination and exploitation", adding that children in Africa and Asia suffered the most.
"More than nine out of 10 children who are not attending school, who are malnourished, and who die before the age of five live in these two continents," she said.
"Exploitation of children is not simply a breach of an international treaty," she said.
"It's pain. It's suffering and confusion and damage. It's hope lost and hope betrayed."