WASHINGTON - The White House said on Thursday that President Barack Obama didn't say violence has ended in Afghanistan although he has sent an apology letter to the Afghan counterpart Hamid Karzai.

In remarks to reporters on board Air Force One, White House spokesman Jay Carney said "nobody has suggested that violence has ended in Afghanistan in general or in reaction to the unfortunate incident involving the inadvertent, unintentional burning of religious materials."

Obama told US broadcaster ABC on Wednesday that his formal apology to Afghan President Hamid Karzai for the burning of Qurans by US troops last week, is aimed at curbing further danger to US troops on the ground.

He said it has "calmed things down" after the incident sparked an outbreak of violence across the country, but the US side is " not out of the woods yet."

Carney said what Obama was trying to convey was "the statements by US leaders had helped calm the situation down."