"Whether it's courage or they changed their mind, I can't tell you," the president added.
Trump had earlier called allies in the Middle East to tell them his decision on recognizing Jerusalem as the capital of Israel and the US administration's intent to move its embassy there.
A Palestinian envoy told Reuters that the decision was a "declaration of war" in the Middle East. Pope Francis called for Jerusalem's "status quo" to be respected, saying new tension would further inflame world conflicts.
British Prime Minister Theresa May had told Parliament earlier that she would be speaking to the US president on his decision on Jerusalem.