"In an instant neighborhoods were destroyed, dozens of people lost their lives, many more were injured," Obama said from the White House State Dining Room. "Among the victims were young children trying to take shelter in the safest place they knew - their school."
The president added that the town of Moore, Okla., "needs to get everything it needs right away."
Obama spoke following a meeting with his disaster response team, including Homeland Security Secretary Janet Napolitano and top White House officials. On Monday, he spoke with Oklahoma Gov. Mary Fallin and Republican Rep. Tom Cole, whose home is in the heavily damaged town of Moore, a suburb of Oklahoma City.
The president has also declared a major disaster in Oklahoma, ordering federal aid to supplement state and local recovery efforts. Federal Emergency Management Agency Director Craig Fugate was due in Oklahoma later Tuesday to ensure that federal resources are being properly deployed.
The state medical examiner's office has revised the death toll from the tornado to 24 people, including seven children. Authorities had said initially that as many as 51 people were dead, including 20 children.
Teams are continuing to search the rubble in Moore, 10 miles south of Oklahoma City, after the Monday afternoon's more than half-mile-wide twister.