(CNN)The US military negotiated a secret arrangement with the Taliban that resulted in members of the militant group escorting clusters of Americans to the gates of the Kabul airport as they sought to escape Afghanistan, two defense officials told CNN.

One of the officials also revealed that US special operations forces set up a "secret gate" at the airport and established "call centers" to guide Americans through the evacuation process.

While one of the military officials said the arrangement with the Taliban "worked beautifully," Americans involved in an unofficial network dedicated to helping Americans and vulnerable Afghans said there were problems -- particularly in the beginning -- as the Taliban turned away US citizens and legal permanent residents the militant group was supposed to allow through.