With the Taliban claiming to have taken control of 85% of Afghanistan – a statement that U.S. government officials continue to dispute – Kirby told "Fox News Sunday" anchor Chris Wallace that the Pentagon was "not unmindful" of the situation.
"We're certainly watching with deep concern, Chris, the deteriorating security situation and the violence, which is of course way too high, and the advances and the momentum that the Taliban seems to have right now," he noted.
Kirby announced that officials are monitoring the Taliban's moves in the country and working alongside the Afghan military "to encourage them to use the capacity and the capability that we know they have, and we know that they know how to defend their country."
He said Afghanistan's capacity and capabilities included a "very capable" Air Force and "very sophisticated" special forces that can help defend the country from the Taliban resurgence.
"This is a time for them to step up and to do exactly that," Kirby said of their Afghan partners.
With U.S. Central Command estimating that over 90% of the withdrawal process is complete, Kirby highlighted that even though U.S. troops will not be supporting Afghanistan on the ground, the U.S. will indeed continue to support the country and its people.
"We are not walking away from this relationship," Kirby insisted. "We’re going to continue to support them from a financial perspective, logistical perspective and certainly aircraft maintenance."
During the 20-year period, American troops trained more than 300,000 Afghan military members and security forces in order to aid them in combating the threat of the Taliban.
At least seven Afghan pilots have been assassinated off base in recent months, according to two senior Afghan government officials.
This series of targeted killings, which haven't been previously reported, illustrate what U.S. and Afghan officials believe is a deliberate Taliban effort to destroy one of Afghanistan's most valuable military assets: its corps of U.S.- and NATO-trained military pilots.
In so doing, the Taliban -- who have no air force -- are looking to level the playing field as they press major ground offensives. The militants are quickly seizing territory once controlled by the U.S.-backed government of President Ashraf Ghani, raising fears they could eventually try to topple Kabul.