The Combined Declares has given Afghanistan the place of "major non-Nato ally".
The status, such as nations such as Modern australia, The red sea and Israel, gives preferential entry to US hands exports and protection co-operation.
The statement was made by US Assistant of Condition Hillary Clinton on an surprise trip to Afghanistan.
It comes prior to a significant donors' meeting in Asia, which is due to talk about aid to Kabul after most Nato-led soldiers keep the nation in 2014.
Participants at Sunday's meeting in Seattle are required to make almost $4bn (£2.6bn) in yearly growth assistance to Afghanistan.
The nation's main financial institution says it needs more than $4bn in aid each season, on top of $4bn for protection causes.
A mature English formal described the process of increasing that money at the Seattle meeting as an unmatched process,
Afghanistan is looking for company responsibilities, but contributors at Tokyo's meeting are also seen as likely to need assures from Kabul on good government and visibility.
Pullout fears
Ms Clinton said after shares with Chief executive Hamid Karzai that giving Afghanistan the new place was a "powerful icon of our investment to Afghanistan's future".
She added: "We are not even visualizing walking away from Afghanistan."
The modify, which comes into impact instantly, makes it much simpler for Kabul to purchase US army devices and makes simpler hands trade techniques.
However, it will be many years before Afghanistan is in a place to buy weaponry for itself, depending as it does on international assistance, the BBC's Mark Loyn in Kabul reviews.
The last nation to be provided significant non-Nato best friend place was Pakistan in 2004.
Nato commanders meeting in Chi town in May recommended programs to hand over fight control to Afghan causes by mid-2013. After the full North athlantic treaty organisation drawback in 2014, only training systems will stay.
At the Chi town meeting, US Chief executive Barack Barack obama released a investment that California would not get away from Afghanistan.
Earlier in May, Mr Barack obama and Mr Karzai finalized a 10-year ideal collaboration contract describing army and municipal connections between the nations after 2014.
