More than half of all countries will likely fail to hit the UN target of reducing premature deaths from a quartet of chronic diseases by a third before 2030, researchers have said.

Cancers, heart and blood-vessel disease, diabetes, and chronic respiratory disease combined to kill 12.5 million people aged 30 to 70 worldwide in 2016, they reported in the NCD Countdown 2030 report, published in The Lancet.

"The bottom line is this: a set of commitments were made, and most countries are not going to meet them," lead author Majid Ezzati, a professor at Imperial School London's School of Public Health, told AFP.

Only 35 nations are on track to meet UN Sustainable Development Goal 3.4 - launched in 2015 - for women, and even less for men, the study revealed.

"International donors and national governments are doing too little to reduce deaths from non-communicable diseases," Prof Ezzati said.

The good news, he added, is that most countries are at least moving in the right direction.

But around 20 states - 15 for women, 24 for men - are either stagnating or backsliding.

That select group of failure includes only one wealthy nation - the United States.

A much-noted study last year in the American Journal of Public Health showed that the rise in premature deaths was especially sharp among white, rural Americans, described by the authors as gripped by an "epidemic of despair".

"It comes down to weak public health, weak health care system, high levels of inequality," Mr Ezzati said.

Across all age groups, non-communicable diseases kill more than 40 million people a year worldwide, accounting for seven-in-ten deaths.

Of these, 17 million are classified as "premature," or before the age of 70.

Only four countries - South Korea, Japan, Switzerland and Australia - ranked among the top ten for lowest NCD mortality rates for both men and women.

Spain, Singapore, Portugal, Italy, Finland and France rounded out the good health podium for women.

For men, the other countries were Iceland, Sweden, Norway, Bahrain, Canada and New Zealand.

The US ranked 53rd for men, and 44th for women, with Chinese men and women placed 80th and 76th, respectively.

China is not on track to meet the goal but its NCD rates are declining, even as levels of obesity and high blood pressure are on the rise, the study revealed.

Smoking rates have stabilised but remain high, especially for men. Tobacco use claims one million lives in China every year.

In sub-Saharan Africa, non-communicable diseases account for a smaller share of deaths than infectious diseases such as AIDS and tuberculosis.

But their NCD mortality rates are still much higher than in most middle-income and rich countries, and should not be neglected, the authors said.