Jozy Altidore underwent an MRI on his injured left hamstring on Tuesday, but results weren't immediately available.
Altidore is the United States' only legitimate option at striker, with Aron Johannsson being a much different player.
"With Jozy, we've got to see how he now reacts the next couple days with his hamstring, and we're full of hope that he comes back still in this tournament, and that's what we kind of work on every day," Klinsmann said. "The medical staff is doing a tremendous job (for) weeks, so we still have to hope that Jozy will be back. How quickly? That is down to his healing process."