Children born in the United States are more likely to die before 20 years old than kids in other wealthy nations, according to new research.

A study revealed that the US has the worst childhood mortality rate compared to 19 other developed countries with children of all ages dying more often since the 1980s.

Researchers found that the main cause of death in American teens was gun violence followed by car accidents, while infants are 76 percent more likely to die than those in other countries.

Despite the US spending more in health care than other nations, experts suggest that keeping kids alive would require the input of multiple sectors.

A graph shows child mortality in the US by age group between 1960-2010

Researchers from Johns Hopkins Hospital in Baltimore, Maryland, analyzed data from 1961 to 2010 from the Human Mortality Database and the World Health Organization's Mortality Database.

They then examined the mortality rates for children up to age 20 in the US and compared them to 19 other developed nations in the Organization for Economic Cooperation and Development (OECD) including Canada, Australia, France, Sweden, and the UK.

In all 20 nations, childhood mortality rates gradually declined in within that 50-year period - a great achievement in public health.

However, the US rate lagged behind the rest.

Between 2001 and 2010 infants were 76 percent more likely to die in the US than other countries.

Within that same decade American children aged one to 19 were 57 percent more likely to die.

The findings published in Health Affairs showed that those aged 15 to 19 were 82 percent more likely to die from gun homicide in the US.

'This study should alarm everyone. The US is the most dangerous of wealthy, democratic countries in the world for children,' said Dr Ashish Thakrar, lead author of the study.

'Across all ages and in both sexes, children have been dying more often in the US than in similar countries since the 1980s,' he added.

Previous research has shown that infants die more frequently in the US, however this is the first study to discover that the trend began decades ago.

In the US the infant mortality rate was 5.9 in 1,000 births in 2015, according to the Centers for Disease Control and Prevention.

'We found that excess deaths in the US are concentrated among infants from causes such as immaturity and SIDS, and among teens, from injuries,' Dr Thakrar said.

Over the fifty-year study period, the lagging US performance amounted to over 600,000 excess deaths.

The 20 countries in the OECD include the US, Australia, Austria, Belgium, Canada, Denmark, Finland, France, Germany, Iceland, Ireland, Italy, Japan, the Netherlands, New Zealand, Norway, Spain, Sweden, Switzerland and the United Kingdom.

'It really seems to be the impact of our fragmented health care system,' Dr Thakrar says.

He suggests that other societal factors such as the rise in childhood poverty in the 1980s may also play a role.

'The care of children is a basic moral responsibility of our society,' wrote the study author.