President Donald Trump said he wanted US troops home from Afghanistan by Christmas, speeding up the timeline for ending America's longest war.
"We should have the small remaining number of our BRAVE Men and Women serving in Afghanistan home by Christmas!" Mr Trump said on Twitter.
In a February 29 agreement reached with the Taliban in Qatar, the United States promised to pull out all its troops by mid-2021 in return for insurgents' promises not to allow Afghanistan to be used by extremists – the original reason for the 2001 US invasion.
After intense US cajoling, the Afghan government and Taliban last month opened peace talks in Doha, although negotiations have quickly deadlocked.
Mr Trump's promise comes only weeks before US elections in which the president, trailing in the polls, has sought to show that he is making good on his promise to draw a close to "endless wars".
Afghan war in pictures
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Sergeant Jay Kenney, 26, with the 101st Airborne Division, Task Force Destiny, assists wounded Afghan National Army (ANA) soldiers off the Blackhawk UH-60A helicopter after they were rescued in an air mission in Kandahar on December 12, 2010 in Kandahar province, Afghanistan. Getty Images -
An Afghan Northern Alliance fighter mans the front line against the Taliban on October 2, 2001 near Jabul os Sarache, 30 miles north of Kabul. Getty Images -
Abdullah Abdullah, chief executive of Afghanistan travelling via helicopter for the final campaign rally in Bamiyan, Afghanistan on September 25, 2019. Afghans will head to the polls on Saturday, September 28th. Getty Images -
Mustafa Tamanna, 10, son of Afghan reporter Zabihullah Tamanna, weeps during the funeral ceremony in Kabul, Afghanistan on June 7, 2016. Tamanna was killed by a rocket-propelled grenade fired by the Taliban. Getty Images -
Northern Alliance soldiers come back from the front line after a battle near Charatoy town in the north of Afghanistan on October 10, 2001. REUTERS -
A Northern Alliance fighter throwing rocks as part of a popular national game yards away from a multiple Grad missile launcher in October 12, 2001 in the Salang Gorge in Northern Afghanistan. Getty Images -
A French soldier from the 7th Mountain Regiment, part of the International Security and Assistance Force (ISAF) stands on a boulder overlooking Kabul during a patrol August 3, 2002 in Afghanistan. The ISAF has been patrolling Kabul since January 2002, working with the government and a new police force to prevent the violence and lawlessness that threatened to engulf the city after a U.S.-led coalition forced the Taliban from power. Getty Images -
US Marine Sgt. Jerry Brown (L) of Jacksonville, North Carolina watches over a weapons cache found during a patrol near the American military compound at Kandahar Airport in January 16, 2002 in Kandahar, Afghanistan. The Marines recovered mortars, rockets, rocket-propelled grenades and artillery rounds discovered in various caches near the base while on the patrol. Getty Images) -
Members of the Princess Patricia's Canadian Light Infantry patrol through poppy fields in the village of Markhanai in May 6, 2002 in the Tora Bora valley region of Afghanistan. Getty Images -
The United States and Britain on October 7, 2001 launched a first wave of air strikes against Afghanistan. President George W. Bush said the action heralded a "sustained, comprehensive and relentless" campaign against terrorism. REUTERS -
A young Afghan girl eats a piece of bread at the Chaman refugee camp on November 8, 2001 on the Pakistan border with Afghanistan. The UNHCR has estimated that since September 11, 2001 over 135,000 Afghans have crossed the border into Pakistan, adding to the already millions of refugees living in the country. Getty Images -
Afghan opposition Northern Alliance soldiers leap over a trench as they return from front line positions after battle near the town of Charatoy in the north of Afghanistan October 10, 2001. REUTERS -
An Afghan child peeks out from the doorway of his family's home as a US Army soldier from the 101st Airborne stands guard in the eastern Afghan village of Hesarak on July 16, 2002 during what the Army refers to as a 'sensitive site exploitation' mission or 'SSE'. Getty Images -
Fred Perry, a British Royal Engineer soldier, reads the book "Black Hawk Down" inside his tent after a day of work on January 29, 2002 at the International Security Assistance Force (ISAF) barracks at the Kabul airport in Kabul, Afghanistan. Getty Images -
Afghan soldiers (L) speak to a local Afghan, while a medic in the U.S. Army's 1st Battalion, 36th Infantry Regiment, Charlie Company (R) monitors a soldier who has just survived a blast from an improvised explosive device (IED) while driving a vehicle during a mission near Command Outpost Pa'in Kalay, on March 19, 2013 in Kandahar Province, Maiwand District, Afghanistan. Getty Images -
Marines on a light armored vehicle prepare for patrol as an AH1W "Super Cobra" helicopter flies by on December 28, 2001 at the U.S. Marine Corps Base in Kandahar, Afghanistan. Getty Images -
A Norwegian ISAF (International Security Assistance Force)soldier from Recce Squadron 3 patrols on October 4, 2004 in Kabul, Afghanistan as election officials get ready for the Presidential elections. Getty Images -
Interim Afghan leader Hamid Karzai (L) is greeted by a group of Afghan military officers on his arrival to Kandahar airbase on May 04, 2002 in Southern Afghanistan. Getty Images -
Soldiers in the U.S. Army's 101st Airborne Division wade though a creek to avoid buried insurgent bombs while on patrol October 16, 2010 in Zhari district west of Kandahar, Afghanistan. Getty Images -
British commandos descend from a mountain observation post overlooking the beginning of the Helmand River at the Kajaki hydroelectric dam on March 13, 2007 in Afghanistan's southern Helmand province. Getty Images -
101st Airbornes 1st Sgt. Kerry Black from Westmoreland, Tennessee uses an Afghan child's sling shot on February 6, 2002 as children crowd around him while he patrols on the outskirts of Kandahar, Afghanistan. Getty Images -
Marine Cpl. Jonathan Eckert of Oak Lawn, IL attached to India Battery, 3rd Battalion, 12th Marine Regiment works his improvised explosive device (IED) sniffing dog Bee as they secure a compound during a patrol near Forward Operating Base (FOB) Zeebrugge on October 11, 2010 in Kajaki, Afghanistan. Getty Images -
Afghan refugees walk across the border into Pakistan on October 11, 2001 as they leave Afghanistan at the Chaman crossing point on the 4th day of U.S.-led air strikes against the ruling Taliban and terrorist networks in the country. Getty Images -
Anti-Taliban Afghan fighters watch several explosions from U.S. bombings in the Tora Bora mountains in Afghanistan on December 16, 2001. -
British Marines run under fire from the Taliban during a morning operation on March 18, 2007 near Kajaki in the Afghan province of Helmand. Getty Images -
Afghan Army troops prepare to board a British chinook helicopter from their base at Shorabak on March 12, 2007 in Southern Helmand province, Afghanistan. Getty Images -
British Marine Joe Harvey from Stafford, England (R), watches as British forces come under fire by Taliban insurgents on March 18, 2007 near Kajaki in the Afghan province of Helmand. Getty Images -
U.S. Army 101st Airborne 3-187 "Bravo" company soliders pass through a corn field while conducting a sensitive site exploitation (SSE) mission July 23, 2002 near the town of Narizah in Southeastern Afghanistan. Getty Images -
Scouts from 2nd Battalion, 503rd Infantry Regiment (Airborne), pull overwatch during Operation Destined Strike while 2nd Platoon, Able Company searches a village below the Chowkay Valley in Kunar Province, Afghanistan on August 22, 2006. US Army
After 19 years of US military operations his stance enjoys broad support at home including from his Democratic rival Joe Biden, who during his time as vice president had pushed to curtail US involvement in Afghanistan.
Asked last month whether he backed Mr Trump's plans to withdraw troops from Afghanistan and Iraq, Mr Biden said: "Yes, I do. As long as he has a plan to figure out how he's going to deal with ISIS", the ultra-violent movement that has been active in both countries.
The US first intervened in Afghanistan following the September 11, 2001 attacks and dislodged the Taliban regime, which had welcomed Al Qaeda.
But in the years since the resurgent militants have launched a fresh battle to topple the US-backed government in Kabul, with civilians bearing the brunt of spiralling violence since Nato combat troops withdrew in 2014.
The former Taliban regime imposed an ultraconservative religious ruling on Afghanistan that banned music and education for girls.
The Doha talks have quickly deadlocked over the Taliban's insistence that negotiations adhere to a strict Sunni school of jurisprudence, a step the government says would discriminate against Shiites and other minorities.
Speaking earlier on Wednesday, the veteran US diplomat who negotiated with the Taliban, Zalmay Khalilzad, nonetheless voiced guarded hope for the talks.
"The overwhelming majority of the Afghans would like to see an end to the conflict," Mr Khalilzad, speaking by video, told a forum of the University of Chicago's Pearson Institute.
"I believe that the Taliban are quite serious about the negotiations. Many thought that they wouldn't sit across the table from the Afghan government – that all they wanted was an agreement for the withdrawal of US forces. But they are now sitting across the table."
Mr Trump has already reduced US forces in Afghanistan to about 8,600 and the Taliban has stood by promises not to attack western troops – even as the militants continue their bloody campaign against government forces.
"The level of violence is too high as far as we're concerned," Mr Khalilzad said, although he asserted that Afghan civilian and military casualties had declined in the first half of 2020.
Afghan President Ashraf Ghani, who visited Doha on Tuesday, called on the Taliban to "have courage" and declare a national ceasefire.
The Trump administration has pressed Mr Ghani's government to release about 5,000 Taliban prisoners, a condition of the militants to start talks.
