The US has named Afghanistan a major non-NATO ally, giving the country a similar security status with Washington as Israel and Japan.
The move will make it easier for Kabul to buy new weapons from the US.
US Secretary of State Hillary Clinton made the announcement during a surprise visit to Afghanistan where she met President Hamid Karzai.
“The United States will be your friend and your partner, we are not even imagining abandoning Afghanistan, quite the opposite: we are building a partnership with Afghanistan that will endure far into the future,” said Clinton.
The status upgrade comes in advance of an expected NATO troop pullout in 2014 and on the eve of a major donor conference in Tokyo where nearly 4 billion dollars of development aid is likely to be pledged.
There are fears of a return to chaos without adequate funding once international forces are withdrawn.
Commentators said the new status was a political statement of support for Afghanistan’s long-term stability.