Though admitting the security situation in Afghanistan was "not going in the right direction," the United States Monday said it was up to Afghan security forces to defend the country after Taliban militants seized several cities over the weekend.

Pentagon spokesman John Kirby said the United States was deeply concerned about the trend but that Afghan security forces had the capability to fight the insurgent group.

"These are their military forces, these are their provincial capitals, their people to defend, and it's really going to come down to the leadership that they're willing to exude here at this particular moment," Kirby told reporters during a briefing.

Asked what the U.S. military can do if the Afghan security forces are not putting up a fight, Kirby said, "Not much."

The U.S. military recently conducted airstrikes against Taliban militants as the insurgent group made rapid advances in the battleground and claimed to have captured six provincial capitals after heavy clashes.

Kirby declined to speculate if the U.S. military will continue to provide air support for Afghan forces beyond August 31, the date that President Joe Biden had ordered the U.S. military to end its mission in Afghanistan.

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Many Afghan cities and about half of the country's 34 provinces have seen heavy battles and street fighting in recent weeks as Taliban militants continued fighting against security forces.

U.S. officials, speaking on condition of anonymity, said while the military had warned Biden earlier this year that provincial capitals would fall with a withdrawal of troops, they were still surprised at how quickly some of them were being taken by the Taliban.

The U.S. State Department on Monday said U.S. Special Representative for Afghanistan Reconciliation Zalmay Khalilzad had left for Doha where he will hold talks on Afghanistan and press the Taliban to stop their military offensive.

Given the deteriorating security situation, the U.S. Embassy in Kabul on Saturday urged all Americans to leave the country immediately via available commercial flights. 

(With input from agencies)

(Cover: An Afghan special force member during a military operation against the Taliban fighters in the Kandak Anayat village of Kunduz city, Afghanistan, July 23, 2021. /Xinhua)