US Defense Secretary Lloyd Austin called Friday for international pressure to force a deal between the Kabul government and the Taliban to end the conflict in Afghanistan.

"The security situation in Afghanistan only argues more for international pressure to have a negotiated political settlement to end this conflict, and give the Afghan people (the) government they want and they deserve," Austin said in a tweet.

"The entire world can help by continuing this push."

Austin made the call a day after US President Joe Biden announced that the US withdrawal from Afghanistan, after nearly two decades of war, would be completed by August 31.

The Pentagon chief did not specify which countries he was urging to help secure a settlement, after a year of fruitless talks in Doha between the two sides.

But Pakistan is widely believed to have significant influence over the insurgents.

And on Wednesday an Afghan government delegation met with Taliban representatives in Tehran, hosted by Iran's Foreign Minister Mohammad Javad Zarif.

"Today the people and political leaders of Afghanistan must make difficult decisions for the future of their country," Zarif said.

Zarif appealed to the warring parties in Afghanistan to return to the negotiating table, calling "commitment to political solutions the best choice for Afghanistan's leaders and political movements."

Austin's call comes as the Taliban insurgents, who were ousted from power in 2001 by the US-led invasion, have steadily gained ground against government forces in a tough offensive that has picked up pace as the US pullout nears completion.

Earlier Friday, they claimed that they had control of 85 percent of the country after seizing key border crossings with Iran and Turkmenistan.

The claim was disputed by the government, saying they have forced the insurgents from the northwestern provincial capital of Qala-i-naw, the scene of tough fighting this week.