A fresh contingent of Marines arrived in Kabul on Saturday as part of a 3,000-troop force intended to secure an airlift of US embassy personnel and Afghan allies as Taliban insurgents approach the outskirts of the capital.

The last-minute decision to re-insert thousands of US troops into Afghanistan reflects the dire state of security and calls into question whether President Joe Biden will meet his August 31 deadline for fully withdrawing combat forces.

After an advance group of Marines arrived on Friday, more flowed into the Kabul international airport on Saturday, said Navy Captain William Urban, a spokesman for the US Central Command. Citing operational security, Urban declined to provide specific numbers. The Pentagon said on Friday that the bulk of the 3,000 — comprising two battalions of Marines and one of Army soldiers — are due by the end of the weekend.

Officials have stressed that the newly arriving troops’ mission is limited to assisting the airlift of embassy personnel and Afghan allies, and they expect to complete it by month’s end. But they might have to stay longer if the embassy is threatened by a Taliban takeover of Kabul by then.

On Saturday, the Taliban seized two more provinces and approached the outskirts of Kabul while also launching a multi-pronged assault on a major northern city defended by former warlords, Afghan officials said.

“Clearly from their actions, it appears as if they are trying to get Kabul isolated,” Pentagon spokesman John Kirby said, referring to the Taliban’s speedy and efficient takedown of major provincial capitals this past week.