District of Columbia: President Barack Obama called his French counterpart Francois Hollande Friday and ordered flags be flown at half-staff in a show of solidarity following the Nice attacks.
Spokesman Josh Earnest said the White House had offered the French authorities "any assistance that they need to conduct their investigation."
Obama has described the truck attack that killed at least 84 people as a "horrific terrorist attack."
He is expected to deliver fuller remarks during a reception for foreign diplomats at the White House later on Friday.
"We`ll be offering our strongest support to the people of France in this very difficult time," said Earnest.
Amid uncertainty about the perpetrator`s motives, the White House said "there`s still much more that needs to be learned about this particular situation."
