The deal, hammered out over months of at times contentious negotiations, covers U.S.-Afghan relations in the spheres of security, governance, and economics and is meant to transition the United States from a foreign presence at war in the country to steadfast partner for a sovereign Afghanistan.
It does not commit Washington to any specific troop presence. But does allow the United States to potentially keep troops in Afghanistan after the war ends for the continued training of Afghan forces and for targeted operations against Al-Qaeda, which is mainly present in neighboring Pakistan.
A White House fact sheet on the agreement underlined that Washington "does not seek permanent military bases in Afghanistan."
The pact also does not commit Washington to any specific level of spending, but it does pledge financial support for Kabul for a decade after the withdrawal of the last 87,000 U.S. soldiers.
The White House fact sheet said the agreement commits Washington to "seek funding from Congress on an annual basis to support the training, equipping, advising and sustaining of Afghan National Security Forces, as well as for social and economic assistance."
"U.S. commitments to support Afghanistan’s social and economic development, security, institutions and regional cooperation are matched by Afghan commitments to strengthen accountability, transparency, oversight, and to protect the human rights of all Afghans – men and women," the White House release said.
At the signing ceremony, which took place just after midnight local time on May 2, Obama said, "Neither Americans nor the Afghan people asked for this war, yet for a decade we've stood together. Today with the signing of the strategic partnership agreement we look forward to a future of peace."
Obama also told Karzai that "there will be difficult days ahead," but said he was "confident Afghan forces will grow stronger and the Afghan people will take control of their future."
On Tuesday evening, Obama arrived Bagram Air base for the unannounced visit before traveling by helicopter to the presidential palace in Kabul for the signing.
He is expected to travel back to Bagram, where he will give a speech designed to reach Americans in the U.S. at the dinnertime hour of 7:30 PM.
White House aides told "The New York Times" that Obama's decision to travel to Kabul to ink the agreement was meant to symbolize that the United States will not abandon Afghanistan after combat troops have left.
The timing of his visit is also highly symbolic, as it comes on the one-year anniversary of the killing of former Al-Qaeda lader Osama bin Laden, who masterminded the 9/11 attacks on the United States.
Since last year's U.S. Navy Seal raid on bin Laden's compound in Abbottabad, Pakistan, ties between Afghanistan and Washington have been tested anew by the burning of Korans at a U.S. base and the massacre of 17 civilians, including children, allegedly by an American soldier.
The incidents have prompted Karzai to call for a quickened withdrawal of U.S. forces from the country.