The US did not inform the Libyan government about the arrest of the suspected ringleader of the 2012 on an American diplomatic compound, according to a Libyan minister.
The US Ambassador to the United Nations, Samantha Power, notified the UN Security Council of the capture on Sunday of Ahmed Abu Khatallah by US special forces.
She said an investigation had not only implicated him in the 2012 raid but also planned "further armed attacks" against US personnel.
More top news
The First Lady's masterly performance, combined with Bernie Sanders' impressive speech, saved a convention that was fraying at the edges.
The High Court will hear a legal challenge to Labour's decision to guarantee Jeremy Corbyn a place on the party's leadership ballot.
Russian Foreign Minister Sergei Lavrov brushed aside accusations that Moscow was behind the hacking of internal Democratic Party memos.