[Watch] Obama in Afghanistan, signs 'strategic pact' with Kabul

U.S. President Barack Obama marked the anniversary of Osama bin Laden's death with an unexpected visit to Afghanistan, signing a strategic pact with Kabul  and delivering an election-year message to Americans that the war is closing to an end.

Shortly after arriving under the cover of darkness, President Obama and Afghan President Hamid Karzai signed a strategic partnership agreement at the Afghan leader's palace that sets out a long-term U.S. role in Afghanistan, including aid and advisers.

The deal may provide Afghans with reassurances that they will not be abandoned when most NATO combat troops leave the embattled country in 2014.

For Obama, it was an opportunity to draw a line under a war started by his predecessor, George W. Bush, in response to the September 11, 2001, attacks on the United States but which is now widely unpopular at home.

"My fellow Americans, we have travelled through more than a decade under the dark cloud of war. Yet here, in the pre-dawn darkness of Afghanistan, we can see the light of a new day on the horizon," Obama said in a televised address to the American people against the backdrop of armoured vehicles and a U.S. flag.

"As we emerge from a decade of conflict abroad and economic crisis at home, it's time to renew America," he said. "This time of war began in Afghanistan, and this is where it will end."

Nearly 3,000 U.S. and NATO soldiers have died during the Afghanistan war since the Taliban rulers were ousted in 2001.

Obama visited with troops during a stay of roughly six hours in the country and emphasized the demise of al Qaeda leader bin Laden, an event that his re-election campaign has touted as one of his most important achievements in office. Obama left Afghanistan on Air Force One shortly after delivering his speech.

"Not only were we able to drive al Qaeda out of Afghanistan, but slowly and systematically we have been able to decimate the ranks of al Qaeda, and a year ago we were able to finally bring Osama bin Laden to justice," Obama said to cheers.

But even as he asserted in his speech that there was a "clear path" to fulfilling the U.S. mission in Afghanistan and made his strongest claim yet that the defeat of al Qaeda was "within reach," he warned of further hardship ahead.

"I recognise that many Americans are tired of war. ... But we must finish the job we started in Afghanistan and end this war responsibly," he said at Bagram airbase outside of Kabul, where only months ago thousands of Afghans rioted after U.S. troops accidentally burned copies of the Koran, the Muslim holy book.