McCain, 68, who will replace David Beasley in April, tweeted that she was “deeply honoured” to take over at the helm of an organisation which has been getting emergency aid to people for nearly six decades.

Beasley tweeted that McCain was taking over in a period when “conflicts, climate shocks & hunger soar”.

The heiress to the Hensley Beverage Company in Phoenix, McCain is the widow of John McCain, the unsuccessful 2008 presidential candidate and Republican US senator from Arizona figure who died in 2018.

She is currently the US’ permanent representative to the UN agencies in the Italian capital.

WFP, which won the Nobel Peace Prize in 2020, provided aid to 158 million people in 2022, and received US$14 billion in funding.

The US is the agency’s largest contributor, ahead of Germany, Canada and Sweden.