WASHINGTON: President Barack Obama says the biggest mistake of his presidency was a lack of planning for the aftermath of the fall of late Libyan leader Moamer Kadhafi, with the country spiralling into chaos and grappling with violent extremists.

Asked in a Fox News interview aired Sunday to name the “worst mistake” of his presidency, the US leader said it was “probably failing to plan for the day after what I think was the right thing to do in intervening in Libya."

Obama has repeatedly acknowledged that the United States and its allies could have done more to prevent Libya's descent into chaos following the NATO-backed uprising that led to Kadhafi's ouster and killing in 2011.

He expressed regret over the handling of the aftermath in a lengthy interview with The Atlantic magazine last month, calling the situation in Libya “a mess."

Obama also sharply criticised British Prime Minister David Cameron and former French leader Nicolas Sarkozy for their roles in the Libya campaign, saying in particular that Cameron became “distracted".

Since Kadhafi's death, Libya has descended into near-anarchy, ruled by rival militias vying for power while the militant Islamic State (IS) group has gained influence in the country.

The head of a UN-backed unity government arrived earlier this month in Tripoli to begin garnering support for his administration.

Asked by Fox News to name the worst moment of his White House tenure, the president said it was the day he traveled to Newtown, Connecticut, after a gunman shot 20 young children and six adult staff members at an elementary school in December 2012.

And his biggest accomplishment? “Saving the economy from a great depression."

And his best day in the White House? “The day that we passed health care reform,” Obama said.

“We sat out on the Truman Balcony with all the staff that had worked so hard on it and I knew what it would mean for the families that I'd met who didn't have health care."

“When asked what he most looked forward to upon leaving office next year, Obama replied: “Being able to take a walk outside."