After an initial contingent landed in the Afghan capital on Friday, the US operation appeared to be picking up pace, as the insurgents closed in on Kabul.

Bill Urban, the spokesman for US Central Command, said soldiers "continue" to arrive, but did not say how many were on the ground so far, nor did he say if evacuations had begun.

Pentagon spokesman John Kirby said Friday that the United States would have the capacity to move "thousands per day" after deploying 3,000 personnel to Kabul before the weekend was through.

As of this week, nearly 4,200 people were still working at the US Embassy in Kabul.

In addition, thousands of Afghans who worked for the United States during its 20-year occupation of the war-wracked country as interpreters or drivers and their families are seeking to leave as soon as possible, fearing Taliban retribution.

Many of them will seek special immigrant visas (SIVs) to remain in the United States.

The US government has said applicants will first go to Qatar, where there are US military doctors, and then relocate many of them to other countries to complete the visa process. Those countries have not yet been identified.

The Pentagon estimates that it will need to evacuate about 30,000 people before it completes its withdrawal from Afghanistan by August 31, a deadline set by US President Joe Biden.

Biden and Vice President Kamala Harris conferred via video conference with their national security team "to discuss the ongoing efforts to drawdown our civilian footprint in Afghanistan, evacuate SIV applicants, and monitor the evolving security situation," a White House official said.

Secretary of State Antony Blinken and Defense Secretary Lloyd Austin were among those present, the official said.

Biden was spending several days at the Camp David presidential retreat, which offers more secure communications and easier access for his aides than his home in Wilmington, Delaware, where he had been vacationing.

Taliban fighters were closing in on Kabul after routing the Afghan armed forces over the past 10 days.

On Saturday, Afghan President Ashraf Ghani pledged to prevent further bloodshed, and said consultations were taking place to try to end the fighting, without offering specifics.