The landslide first buried 300-400 homes in an Afghan village, and then hundreds of rescuers from a nearby village, for a total of at least 2,000 deaths, CNN reported Saturday.
Afghan authorities are focusing now on 4,000 survivors and evacuees.
Relief agencies are rounding up food, water, medical support, counselors and emergency shelter, according to a U.N. Assistance Mission in Afghanistan spokesman.
“President Obama affirmed the support of the American people as the Afghans respond to this tragedy and offered additional U.S. assistance to the ongoing relief efforts,” the statement said.
The call is significant, given a strained relationship between Obama and Karzai. The two had not spoken for about eight months before they spoke last in February.
Obama also expressed support for the recent April 5 presidential elections and reaffirmed that the U.S. supports a “sovereign, stable, unified and democratic Afghanistan, the statement said.