Almost one in five US voters know nothing of the extreme hunger currently threatening the lives of 20 million people in Africa and the Middle East, a poll has revealed.

Research commissioned by the International Rescue Committee (IRC) shows that 18% of those polled know nothing of the hunger crises affecting Yemen, Somalia, South Sudan and Nigeria, while a further 28% know little.

Described by the IRC and United Nations as the biggest humanitarian crisis to face the planet since the Second World War, only 15% know "a lot" about the issue while 39% have "some" knowledge".

The IRC said extreme hunger affecting the world had become one of the "least reported but most important major issue of our time".

Of all generations in the US, millennials – those born roughly between 1983 and 1998 – were found to be the most concerned about solving the crisis, the IRC study found.

"More than any other group of Americans, millennials recognise the severity of the hunger crisis and are ready to take on the responsibility of being members of a global community," said former UK Foreign Secretary David Miliband, president and CEO of the IRC.

"In a world that is connected now more than ever, their values are guiding them to step up, and use their voices and their activism to call attention of all age groups to this crisis."

John Della Volpe, who serves as head of polling at the Harvard Kennedy School Institute of Politics, directed the poll of 1,351 registered voters between 29 June and 5 July.

"Since 2001, our polling has consistently found that millennials seek tangible ways to make an impact in their community, country and the world," he said.

"We can clearly see through these new results that America's largest generation is ready to engage on one of the world's greatest challenges and save the lives of tens of millions of people at risk of starvation."

A deadly combination of drought and conflict has led to a severe food shortage in Yemen, Somalia, South Sudan and Nigeria.

The IRC says "drastic cuts" to the US foreign aid budget proposed by the Trump administration for 2018 could more than double the impact of famine.

Its polling, published on Wednesday (12 July), suggests 68% of Americans believe foreign aid from wealthy nations like the US is needed now more than ever.