Updated: 4:00 p.m.

President Barack Obama landed in Afghanistan today for an unannounced visit during which he plans to sign a strategic partnership agreement with Afghan President Hamid Karzai.

Obama flew to the country overnight, according to the pool reporter traveling with the presidential delegation. The president plans to address the American people from Bagram Air Field later today. He is scheduled to sign the 10-page agreement pledging U.S. support for Afghanistan for 10 years after 2014 — the date when NATO forces plan to pull back from their combat role.

The administration has laid out a timeline to significantly reduce American military presence in the embattled county by this fall, pulling back the surge of troops stationed there by the end of September.

According to the pool report, Obama’s “whirlwind” trip began when Air Force One took off from Andrews Air Force base just after midnight EST. He landed at Bagram Air Field around 10 p.m. local time. Obama then traveled to the presidential palace to meet with Karzai.

The middle-of-the-night events, according to senior administration officials, were scheduled both because of security reasons and so that the president’s speech would occur during a convenient hour for American television. The signing will occur around midnight local time and the address will air around 4 a.m. in Afghanistan.

The trip’s details had been embargoed for the president’s safety, as he is in a country where American troops have been at war for nearly a decade.

The visit comes on the one-year anniversary of the U.S. military raid that resulted in the death of terrorist mastermind Osama bin Laden in Pakistan. Senior administration officials acknowledged that the trip coincided with the anniversary but said the timing of the trip was driven more by negotiations on the strategic partnership agreement and both presidents’ desire to sign the agreement in advance of this month’s NATO summit in Chicago.

Obama’s speech is expected to include remarks on the bin Laden anniversary, according to the pool report. The president is also expected to address troops in Afghanistan before he addresses the American people.

Senate Armed Services Chairman Carl Levin (D-Mich.), on a planned trip to the region, stated today via Twitter that he “was honored to be in Kabul [with] President Obama to witness signing of historic partnership with Afghanistan.”

According to the pool report, American Ambassador to Afghanistan Ryan Crocker and Lt. Gen. Mike Scaparotti, deputy commander for U.S. forces in Afghanistan greeted Obama upon arrival at Bagram.