Message of solidarity comes as evidence emerges federal fund shortages stalled storm shelter building plans.
President Barack Obama vowed that the United States would stand behind Oklahoma as it struggled to fill the "empty spaces" left by the devastating tornado with "love and laughter and community".
The President promised the full support of the federal Government and that he would "back up those prayers with deeds for as long as it takes".
Yet even as Obama spoke at the White House, it emerged that shortages of federal funds had derailed Oklahoma authorities' plans to help residents build storm shelters.
Oklahoma City suspended a programme to subsidise safe rooms "due to insufficient federal funding" while the destroyed city of Moore put its plans "on hold" while it battled through a maze of red-tape regulations.