"We don't know that. There are options and we will explore those and the president will ultimately decide," said Pentagon spokeswoman Dana White, adding that the US Army was taking the lead in creating options for the event.
The White House has asked the Pentagon to explore a celebration of "America's great service members," after the Republican president marvelled at the Bastille Day military parade he attended in Paris last year.
Critics have argued that a parade could cost millions of dollars, at a time the Pentagon wants more stable funding for an overstretched military.
When asked who would pay for the cost of the parade, White said the Pentagon was still in the planning phase.
On Wednesday, the Council of the District of Columbia ridiculed the idea of a parade on Pennsylvania Avenue, the 1.2-mile (1.9-km) stretch between the Capitol and the White House that is also the site of the Trump International Hotel.
"Tanks but no tanks!" it tweeted.
One option under consideration is for a parade on November 11 - which would be the 100th anniversary of the end of World War One.
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