Failure to prepare for Muammar Gaddafi's downfall was 'worst mistake' of presidency says Obama

President Barack Obama has admitted that failure to predict and deal with the chaos after the downfall of Libyan strongman Muammar Gaddafi was the "worst mistake" of his presidency.

Though he believes the NATO-led intervention and US military strikes in Libya was "the right thing to do," he also admitted in an interview with Fox News that "failure to plan for the day after" Gaddafi went down was his biggest mistake.

The US and its allies were unprepared for the chaos that followed with militias taking over and two rival parliaments and governments forming, said Obama. That is when the Islamic State (Isis) gained a foothold. Gaddafi died in October 2011, months after the intervention.

At the time the White House seemed pleased with the limited extent of its intervention, which centered on sharing the burden with its European allies, avoided the use of US ground troops, and left the toppling of Gaddafi to Libyans.

Earlier in March Obama described Libya as "a mess" despite also emphasising that the "intervention went as well" as he had hoped. The US leader also criticised France and the UK and in a rare rebuke, he said British Prime Minister David Cameron became "distracted by a range of other things" after the intervention. He said he had more faith in European leaders "being invested in a follow-up," given their geographical "proximity."

National Security Council spokesman Ned Price tried to soften the blow of those words, by telling CNN: "Prime Minister Cameron has been as close a partner as the president has had, and we deeply value the UK's contributions on our shared national security and foreign policy objectives which reflect our special and essential relationship."

Obama had previously said that "all of us — including the United States — could have done more in the aftermath of the Libyan intervention."

In the Fox interview, Obama said his biggest accomplishment was "saving the economy from a great depression" after the 2008 financial crisis. His best day in office was getting his health care reforms passed.

The president revealed that his worst moment came as he travelled to Newton, Connecticut, after 20 children were shot dead at Sandy Hook elementary school.