The United States is expected to keep roughly 650 American troops in Afghanistan to provide security for diplomats after the main US military force completes its withdrawal, which is set to be largely done in the next two weeks, US officials told The Associated Press on Thursday.

In addition, several hundred additional American forces will remain at the Kabul airport, potentially until September, to assist Turkish troops providing security, as a temporary move until a more formal Turkey-led security operation is in place, the officials said.

Overall, officials said the US expects to have American and coalition military command, its leadership and most troops out by July Fourth, or shortly after that, meeting an aspirational deadline that commanders developed months ago.

The officials were not authorized to discuss details of the withdrawal and spoke to AP on condition of anonymity.

AP reported the departure of the bulk of the more than 4,000 troops that have been in the country in recent months is unfolding well before President Joe Biden’s September 11 deadline for withdrawal. And it comes amid accelerating Taliban battlefield gains, fueling fears that the Afghan government and its military could collapse in a matter of months.

In a statement Thursday night, Pentagon press secretary John Kirby said that as Biden has ordered, the US will complete the withdrawal by early September. “Nothing has changed about that goal.” Kirby said.

“The situation is dynamic, and we review our progress daily. Speculation by unnamed sources about potential changes to that timeline should not be construed as predictive.”

On Friday, Afghan President Ashraf Ghani and Abdullah Abdullah, chair of the High Council for National Reconciliation, are meeting with Biden at the White House. The two Afghan leaders also are to meet at the Pentagon with Defense Secretary Lloyd Austin and possibly other administration officials, the Pentagon announced.

AP reported that getting most troops out by early July had been in doubt because of complications including an outbreak of COVID-19 at the US Embassy and the push to get Afghan interpreters and others who helped the US out of the country.

Officials said US commanders and NATO allies in Afghanistan have been able to overcome logistical hurdles that might have prolonged the withdrawal process. But they also warned that plans in place for the final stages of the US military withdrawal could change if airport security agreements fall through or there are other major, unforeseen developments.

AP reported that as recently as last week, there was discussion of possibly extending the US troop presence at Bagram Airfield, north of Kabul, but officials said the US presence at the base is expected to end in the next several days.

The roughly 650 US troops that are planned to be a more permanent force presence in Afghanistan will provide security for the US Embassy and some ongoing support at the airport, AP reported.

Officials also said the US has agreed to leave a C-RAM — or Counter-Rocket, Artillery, Mortar system — at the airport, as well as troops to operate it, as part of an agreement with Turkey. The US also plans to leave aircrew for helicopter support at the airport.

According to the officials, Turkey has largely agreed to provide security at the airport as long as it receives support from American forces. U.S. and Turkish military officials are meeting in Ankara this week to finalize arrangements.