Protecting President-elect Donald Trump and his family is costing New York City more than $1 million a day, according to three city officials, CNN reports. 

And those costs won't necessarily drop significantly once he moves to the White House.

That's because Melania Trump and their 10-year old son Barron expect to stay at their home at Trump Tower in midtown Manhattan, at least until the end of the school year. And Donald Trump has indicated he plans to return home regularly, especially while they're still here.

Adding to the expense is the cost of police assigned to Trump's adult children and his grandchildren, who are also receiving Secret Service protection, John Miller, NYPD's deputy commissioner of intelligence & counterterrorism, told WCBS Monday. All of them live in the city, and all are entitled to receive Secret Service protection.

"The number one imperative here is safety and security. We owe that to the president elect, his family and his team," said New York Mayor Bill de Blasio at a press conference on Friday. But he added the city will need help with those costs, particularly police overtime.

"This is a very substantial undertaking. It will take substantial resources," he said. "We will begin the conversation with the federal government shortly on reimbursement for the NYPD for some of the costs that we are incurring."

While primary responsibility for the protection of the president, or president-elect, rests with the Secret Service, local law enforcement is charged with assisting them, particularly in controlling movements of the general public.

Every president is required to have local law enforcement protection when they return home during their terms. But protecting Trump in New York City is particularly costly, given that he lives in the most densely-populated neighborhood of the nation's biggest city.