Washington | US President Joe Biden’s imperiled re-election campaign sank even further on Wednesday (Thursday AEST) as key donors and senior leadership added to mounting doubts about his ability to beat Donald Trump and serve out another four years.

Hoping to bolster his image via this week’s hosting of the North Atlantic Treaty Organisation (NATO), Mr Biden instead watched as high-profile Democratic financial powerhouse and Hollywood actor George Clooney pulled his support, saying the 81-year-old president no longer had what was required to run the Oval Office.