Biden warns Taliban of 'swift response' as more US troops deploy to Afghanistan

President Joe Biden on Saturday doubled down on his decision to withdraw US forces from Afghanistan despite the Taliban's rapid advances, but pledged to send more troops to evacuate civilians and warned the insurgents not to threaten that mission.

After consultations with his national security team, Biden said a total of "approximately 5,000" US soldiers - up from 3,000 - will now help organise evacuations and the end of the US mission after 20 years on the ground.

He warned the Taliban that any action "that puts US personnel or our mission at risk there, will be met with a swift and strong US military response."

Biden's announcement came after Taliban insurgents captured the main northern holdout city of Mazar-i-Sharif and continued their rapid march towards the capital Kabul.

Afghan President Ashraf Ghani pledged on Saturday not to let the "imposed war on people cause more deaths," and said consultations were taking place to try to help end the war, without offering details.

US Secretary of State Antony Blinken, who was part of the team that conferred with Biden, spoke by telephone with Ghani on Saturday, his spokesman said.

"They discussed the urgency of ongoing diplomatic and political efforts to reduce the violence," spokesman Ned Price said.

Blinken was also expected to "engage with key regional stakeholders" on the escalating Taliban march on Kabul, Biden said.

Earlier, US Central Command said more American military personnel had arrived in Kabul to ensure the safe evacuation of American embassy employees and Afghan civilians who worked for US forces.

The Pentagon estimates it will need to evacuate about 30,000 people before it completes its withdrawal from Afghanistan by August 31, a deadline set by Biden.

Biden's decision to pull troops out of Afghanistan has come under increased scrutiny given the implosion of the country's armed forces, but he said he had no other choice - and laid some of the blame at the feet of Donald Trump.

"When I came to office, I inherited a deal cut by my predecessor... that left the Taliban in the strongest position militarily since 2001 and imposed a May 1, 2021, deadline on US forces," Biden said.

"I faced a choice - follow through on the deal, with a brief extension to get our forces and our allies' forces out safely, or ramp up our presence and send more American troops to fight once again in another country's civil conflict," he added.

"I was the fourth president to preside over an American troop presence in Afghanistan - two Republicans, two Democrats. I would not, and will not, pass this war onto a fifth," Biden said.