The Afghan president's office says it has received a letter from US President Barack Obama formally apologizing for the burning of Quran at a US military base in Afghanistan. The statement from President Hamid Karzai's office says the U.S. ambassador delivered the letter on today. In the letter, which is quoted in the statement, Obama expresses his "deep regret for the reported incident" and offers his "sincere apologies." According to the statement, Obama wrote: "The error was inadvertent; I assure you that we will take the appropriate steps to avoid any recurrence, to include holding accountable those responsible."