"I won't call them monsters because they'd like that term. They'd think that's a great name," he added.
The remarks came as Trump met with Palestinian President Mahmoud Abbas in Bethlehem, where the two are expected to discuss a possible peace deal in the Middle East.
"And interesting that our meeting took place on this horrible morning of death to innocent young people,” Trump said. “Peace can never take root in an environment where violence is tolerated, funded and even rewarded. We must be resolute in condemning such acts in a single unified voice.”
Revisiting remarks from his address to Muslim leaders in Saudi Arabia on Sunday, Trump again called for nations to “drive out” extremists and terrorists from their societies.
“We cannot stand a moment longer for the slaughter of innocent people and in today’s attack it was mostly innocent children,” Trump said. “The terrorists and extremists and those who give them aid and comfort must be driven out from our society forever.”
ABC News' Alexander Mallin contributed to this report.