Taliban forces have taken at least five provincial capitals in the country and others are threatened, Kirby said, adding that the fighting in the country "is clearly not going in the right direction". 

He said Secretary of Defense Lloyd Austin shares the concerns of other nations about the situation. 

Still, he believes "that the Afghan forces have the capability, they have the capacity to make a big difference on the battlefield," Kirby said. 

"He has maintained that we will continue to support them with the authorities we have, where and when feasible � understanding that it's not always going to be feasible." 

This support includes airstrikes and over-the-horizon counterterrorism support. 

While most US forces have withdrawn from Afghanistan, the Defense Department has been centred on carrying out President Joe Biden's order to complete the retrograde from that country by the end of the month. 

The US will then switch to a bilateral relationship with the Afghan government, Kirby said. 

The US has authorities needed to continue air support to the Afghan government through the end of the month, Kirby said. 

"Whatever the outcome here, when we look back, we're going to be able to say that it was driven by leadership � Afghan leadership, political and military leadership," he said. 

"That's what's vital here." 

The Afghan government has a force of over 300,000 soldiers and police, Kirby said. 

The Afghan military has an air force, which the US continues to support and improve. The government forces have modern weaponry and an organisational structure. 

"(The government has) a lot of advantages that the Taliban don't have," Kirby said. 

"The Taliban doesn't have an Air Force, they don't own airspace. (The government forces) have a lot of advantages. Now they have to use those advantages, to exert that leadership. And it's got to come both from the political and from the military."