A proclamation released by the White House on Sunday says the nation shares "in the pain and suffering of all those who were injured in these two senseless attacks."
The first attack Saturday at a shopping area in El Paso, Texas, killed at least 20 people. That was followed by another shooting in a nightlife district in Dayton, Ohio, which claimed nine lives.
Trump has been out of public view since both shootings. He has reacted to the attacks on Twitter.