KABUL (BLOOMBERG) - The US embassy staff in Kabul has been told to start destroying sensitive material, underscoring that the Biden administration is preparing for the possibility that the embassy will be overrun by the Taleban despite public assurances that the building remains in operation.

The management notice to all American personnel, sent early on Friday from the embassy facilities manager, asks staff to "reduce the amount of sensitive material on the property," according to a copy obtained by Bloomberg News.

It asks that they destroy anything with US logos, flags "or items which could be misused in propaganda efforts".

The email details the ways diplomats can destroy material: Use burn bins and shredders for paper, a disintegrator for electronics, incinerators for medical waste and a compactor that "can crush items that are too big for the disintegrator."

It says the embassy will offer what it calls "destruction support" between 8.30am and 4pm until further notice.

"These destruction methods are not appropriate for weapons, ammunition and similar items," it reads.

Two administration officials, who discussed the internal memo on condition of anonymity, said the destruction procedure is standard when a US outpost abroad is being scaled down.

One of the officials said it is consistent with established plans for most US forces in Afghanistan to depart by the end of the month but acknowledged the Taleban's advances played a role.

Pentagon spokesman John Kirby told reporters on Friday that it appears the Taleban is "trying to get Kabul isolated" but that the capital city was not under "imminent threat."

He said the speed at which the Taleban has taken over provincial capitals is "deeply concerning."

The first of 3,000 troops being brought in to help evacuate many of the embassy's employees have arrived.

State Department spokesman Ned Price said at a briefing on Thursday that the embassy remains open for now.

"This is not abandonment, this is not an evacuation, this is not a wholesale withdrawal," Price said.

The Taleban took three more cities across Afghanistan on Friday, adding to the tally of major population centers they have taken in recent days.

The US has been similarly surprised - and frustrated - by the Afghan army's inability or, in some cases, unwillingness, to fight back. Many fighters and officials have given up their weapons and surrendered to the Taleban.