Trump had said in July that the new ballroom "won’t interfere with the current building." But this week he clarified that "to do it properly, we had to take down the existing structure."
Ukraine's leader has estimated that more than 200,000 Ukrainian children have been deported to Russia or territories it controls since the war began more than three years ago.
The president has presented a 20-point plan that would end the war in Gaza, which the leaders of Israel and several other key countries in the region support.
The president posted on Truth Social after he met with Ukrainian President Volodymyr Zelenskyy on the sidelines of the United Nations General Assembly in New York.
Waltz's confirmation also comes just days before world leaders are set to gather for the annual U.N. General Assembly in New York amid multiple major conflicts.