By Amie Parnes - 02/23/12 02:38 PM EST
President Obama wrote a letter this week to formally apologize for the burning of Qurans at a U.S. military base in Afghanistan.
In the letter, written to Afghan President Hamid Karzai, Obama said he wanted to "express my deep regret for the reported incident."
The letter comes on the heels of violent demonstrations in Afghanistan this week, where at least half a dozen Afghans were killed and dozens were injured. On the third day of protests, two U.S. troops were also shot to death, according to news reports.
Tommy Vietor, a National Security Council spokesman said the letter to Karzai followed up on the two leaders' Feb. 20 phone call "to continue their discussion on a range of issues related to our long-term partnership."
Vietor said the letter was delivered by U.S. Ambassador to Afghanistan Ryan Crocker on Thursday afternoon in Kabul.
While the White House did not release the letter, Vietor said Obama "expressed our regret and apologies over the incident in which religious materials were unintentionally mishandled at Bagram Airbase."