"Probably failing to plan for the day after what I think was the right thing to do in intervening in Libya," Obama told the Fox News channel in an interview broadcast on Sunday, commenting on his worst mistake during two presidential terms.
The US leader added that the state of affairs in Libya after the 2011 toppling of the country's leader Muammar Gaddafi was a "mess."
Libya has been in a state of turmoil since the 2011 Arab Spring movement, which later led to a civil war and the overthrow of Gaddafi by Western-supported Islamic extremists.
The Obama administration backed the use of NATO air power in Libya to ensure that rebels topple the then leader after a 2011 revolt. Since Gaddafi’s death the influence of extremist Islamist groups in the country has steadily grown.