US President Barack Obama has paid tribute to the four Americans killed in Libya earlier this week.
Obama was speaking as the bodies of the late US ambassador to Libya, Chris Stevens, and three of his colleagues, arrived at Andrews Air Force Base in Maryland.
Ambassador Stevens and his staff died after gunmen stormed the US consulate in Benghazi, amid a wave of global protests over an anti-Islamic film.
Obama spoke about the four victims in deeply personal terms, saying the US would never "retreat from the world". He said the attack was a reminder of the danger facing Americans in diplomatic and military service.