“You’ve got to be pretty careful with the tanks because the roads have a tendency not to like to carry heavy tanks,” Mr. Trump said, acknowledging the damage that such heavy vehicles could do to Washington’s transportation network. “So we have to put them in certain areas.”

The president did not say where those areas would be.

Pentagon officials declined to comment on Monday as they wrestled with how to accommodate the president’s tank request only a few days before the event. Among the logistical concerns was how to transport tanks that weigh more than 60 tons into the popular downtown area where tourists gather to see the monuments. Moving and guarding the tanks would require staffing at a time when many troops are at home for the holiday.

Another problem is that Arlington Memorial Bridge, which spans the Potomac River and connects Arlington National Cemetery and the Lincoln Memorial, might not be able to hold the weight.