President Barack Obama has expressed condolences to Afghan President Hamid Karzai about his brother's murder.
White House spokesman Jay Carney said Obama telephoned Hamid Karzai on Wednesday morning.
Karzai's half-brother, Ahmed Wali Karzai, was gunned down Tuesday by a close associate.
Thousands of people joined the Afghan president for the funeral ceremony in Kandahar, in southern Afghanistan, on Wednesday.
The killing leaves a void in the southern part of the country as the Afghan government pursues peace talks with insurgents prior to the withdrawal of tens of thousands of U.S. troops by next summer.