Kabul, May 2 (IANS): The US President Barack Obama signed a cooperation agreement with Afghanistan as he paid an unannounced visit to the war-torn country Tuesday on the first anniversary of the killing of Al Qaeda's ex-chief Osama bin Laden in Pakistan.

"Afghanistan has a friend and a partner in the United States," said Obama before he and Afghan President Hamid Karzai signed the Strategic Partnership Agreement outlining cooperation between their countries once the US-led international force withdraws in 2014, CNN reported.

Obama, on his third trip to Afghanistan since taking office, also addressed troops at Bagram Air Field.

During he signing ceremony, the US president said neither country asked for the war which began over a decade earlier, but now they would work in partnership for a peaceful future.

Talking about the concern in Afghanistan that the US would abandon the country once its troops leave, Obama said, "With this agreement, I am confident that the Afghan people will understand that the United States will stand by them."

The US "did not come here to claim resources or to claim territory, he said, adding "We came here with a very clear mission to destroy Al Qaeda," referring to the terrorist organisation responsible for the Sep 11, 2001 attacks.

Obama's visit to Afghanistan came a week after the Afghan and US governments finalised the US-Afghan strategic pact's draft.

The agreement, which paves the way for a long-term US military presence in Afghanistan after the withdrawal of the NATO-led coalition force from the country by 2014, has been welcomed by local analysts as a security stabilising factor in Afghanistan.

At present, there are over 90,000 US troops in Afghanistan and the US is expected to draw down that number to 65,000 by the end of 2012 and to less than 20,000 by the end of 2014.