More of the world's children are surviving to their fifth birthday, but 6.3 million still died last year, mostly from preventable causes, the U.N. children's agency said Tuesday.

That's nearly 17,000 young children dying every day. And while death rates have been cut in half since 1990, the world still is short of meeting a goal of a two-thirds decrease in child mortality by next year, the report by the United Nations Children's Fund said.

"We're building momentum in many countries in the poorest parts of the world," said Dr. Mickey Chopra, UNICEF's head of global programs. The challenge is to spread what works.

India and Nigeria together accounted for more than a third of all the deaths, with their large populations. The world's highest rate of child mortality was in Angola, with 167 deaths for every 1,000 live births. By region, the greatest burden is in sub-Saharan Africa, with a rate of 92 deaths for every 1,000 live births.

By comparison, the U.S. rate is 7 deaths for every 1,000 live births.

But a country's economic status doesn't mean it can't make progress, the report stressed. Every region has made major gains since 1990. It found that eight of the 60 countries with particularly high child mortality had lowered their rates by more than two-thirds since 1990: Malawi, Bangladesh, Liberia, Tanzania, Ethiopia, East Timor, Niger and Eritrea.

The 6.3 million figure is around 200,000 fewer deaths than in 2012.

Pneumonia, diarrhea and malaria account for about a third of all the under-age-5 deaths, the report found.

Chopra told The Associated Press that pneumonia and diarrhea are so widespread because they are easily transmittable. But he said those illnesses, along with malaria, are easily preventable with relatively inexpensive antibiotics. "It is very, very easy to prevent those three diseases from killing kids," Chopra said. "An antibiotic is 10, 20 cents, and that saves the life basically."

Newborns, in the first month of life, make up 44 percent of the deaths. "We're making much faster progress with the older children," Chopra noted.

But some simple interventions can help, he said, including newer vaccines against childhood diarrhea and pneumonia.

For newborns, early breastfeeding and skin-to-skin contact, also called kangaroo care, are hugely important, Chopra added. Even in parts of Africa and Asia where women are more likely to give birth at home, families may swaddle the infant rather than letting mom's body warm the baby and, by resting on her chest, allowing for breastfeeding on demand.

How do poor countries take the steps needed to lower child mortality? In a second report issued Tuesday, researchers took a close look at 10 low- and middle-income countries that are making progress - and found that specific health programs, such as vaccinating children or having skilled health workers at childbirth, account for only half of those countries' improvements.

Importantly, there was no one formula for success. The Success Factors project examined Bangladesh, Cambodia, China, Egypt, Ethiopia, Laos, Nepal, Peru, Rwanda and Vietnam, and found a variety of strategies tailored to different populations.

In Nepal, for example, thousands of female health volunteers visit homes to give immunizations, family planning materials and information on infant care.

In Peru, more women are giving birth in hospitals or birthing clinics.

But things like clean water, improved sanitation and better roads are key to those health efforts, the report found.

"It is not enough to know where a clinic is. You also need roads to get there," noted lead researcher Shyama Kuruvilla of the World Health Organization's Partnership for Maternal, Newborn and Child Health, which coordinated the project.

Educating girls and increasing women's participation in politics and the workforce played a role, too, the Success Factors project concluded.

"They can get a job and earn and have the resources to assure the health of themselves and their families," Kuruvilla explained.

In Rwanda, for example, 64 percent of parliamentarians are women, and China, Bangladesh, Cambodia and Vietnam have developed industries that employ more women, the report said. UNICEF likewise found newborn mortality rates lower for educated mothers.

Both health and social programs are necessary, said UNICEF's Chopra.

Educating a woman so that she knows her infant needs vaccination doesn't help if there are no vaccines, but "it can't just be all about delivery of things. It has to be about empowering people to demand the things," he said.