There've been months of negotiations between the US and the Taliban to try to end the conflict and reach a peace deal in Afghanistan.
President Donald Trump has often said that he's keen to bring soldiers home from America's longest-running war.
We are working to finally end America’s longest war and bring our troops back home.
So we've been looking at how much the US has spent in Afghanistan since the war began.
What forces did the US send?
The US invaded Afghanistan in October 2001 to oust the Taliban, whom they said were harbouring Osama bin Laden and other al-Qaeda figures linked to the 9/11 attacks.
US troop numbers in Afghanistan grew as Washington poured in billions of dollars to fight a Taliban insurgency and fund reconstruction.
Between 2010 to 2012, when the US for a time had more than 100,000 soldiers in the country, the cost of the war grew to almost $100bn a year, according to US government figures.
As the US military shifted its focus away from offensive operations and concentrated more on training up Afghan forces, costs fell sharply.
Between 2016 and 2018 annual expenditure was around $40bn, and the estimated spend for 2019 (up to September) is $38bn.
According to the US Department of Defense, the total military expenditure in Afghanistan (from October 2001 until September 2019) was $778bn.
In addition, the US State Department - along with the US Agency for International Development (USAID) and other government agencies - spent $44bn on reconstruction projects.
That brings the total cost - based on official data - to $822bn since the war began in 2001, but it doesn't include any spending in Pakistan, which the US uses as a base for Afghan-related operations.
An independent study carried out by Brown University's Cost of War Project argues that the official US figures for the Afghan war are a substantial underestimate.
It says that Congress has approved funds amounting to about one trillion dollars for Afghanistan as well as for Pakistan.
Neta Crawford, co-director of the Cost of the War Project, also says this "does not include any of the other costs for war veterans' care, money spent on other government departments for war-related activities and the cost of interest on debt incurred to pay for the conflict,"
If you factor this in, the cost is closer to two trillion dollars, she adds.
Where has the money gone?
The bulk of the money has been spent on counter-insurgency operations, and on the needs of US troops such as food, clothing, medical care, special pay and benefits.
Official data shows the US has also contributed approximately $137bn -16% of all money spent in the last 18 years - to reconstruction efforts in Afghanistan.
And more than half of that ($86bn) has gone on building up Afghan security forces, including the Afghan National Army and police force.
The rest has been mainly spent on improving governance and infrastructure, as well as on economic and humanitarian aid and anti-drug initiatives.
The US has spent on average $1.5m day - or nearly $9bn since 2002 until September last year - on anti-narcotics efforts, yet UN figures show that the total estimated area devoted to opium poppy cultivation reached a record high in 2017.
In 2017, the US watchdog responsible for the oversight of reconstruction efforts said that as much as $15.5bn had been lost on "waste, fraud and abuse" over the past 11 years.
That figure is probably "only a portion" of the total waste, according to the watchdog, which added that US money "often exacerbated conflicts, enabled corruption, and bolstered support for insurgents".
What about the human cost?
Since the war against the Taliban began in 2001, US forces have suffered more than 2,300 deaths and around 20,660 soldiers injured in action.
According to official figures, approximately 13,000 US military personnel were in Afghanistan as of December 2019, but there were also nearly 11,000 US civilians who were working as contractors.
But US casualty figures are dwarfed by the loss of life among Afghan security forces and civilians.
President Ghani said last year that more than 45,000 members of the Afghan security forces had been killed since he became president in 2014.
Mr Ghani's decision to reveal casualty figures was unusual as the US and Afghan governments don't normally publish Afghan death tolls.
However, some media reports say that in recent years Afghan security force fatalities have been very high, sometimes averaging 30-40 deaths a day.
And according to the United Nations Assistance Mission in Afghanistan (Unama), more than 100,000 civilians have been killed or injured since it began systematically recording civilian casualties in 2009.