US President Barack Obama has said failing to prepare for the aftermath of the ousting of Libyan leader Col Muammar Gaddafi was the worst mistake of his presidency.
Mr Obama was answering a series of questions on the highs and lows of his time in office on Fox News.
He said, however, that intervening in Libya had been “the right thing to do”.
The US and other countries carried out strikes designed to protect civilians during the 2011 uprising.
But after the former Libyan leader was killed, Libya plunged into chaos with militias taking over and two rival parliaments and governments forming.
So-called Islamic State (IS) gained a foothold, and Libya became a major departure point for migrants trying to reach Europe.
A UN-backed national unity government arrived in the capital Tripoli earlier this month but is waiting to take charge.
The leader of the faction ruling western Libya has threatened to prosecute any of his ministers who co-operate with the UN-backed administration, contradicting an earlier announcement the ministers would stand down.
President Obama gave the brief but revealing answer speaking to Chris Wallace:
CW: Worst mistake?
Obama: Probably failing to plan for the day after, what I think was the right thing to do, in intervening in Libya.
It is not the first time President Obama has expressed regret over Libya. He toldthe Atlantic magazine last month the operation went as well as he had hoped, but Libya was now “a mess”.