President Donald Trump could withhold nearly $27 billion from sanctuary cities as a penalty for harboring illegal immigrants, a nonprofit group reported Friday.

"We sourced nearly $27 billion to sanctuary cities in federal grants and direct payments" in 2016, a report by the accountability group Open The Books said.

"The vast majority of federal monies fund critical infrastructure in major cities like housing, education, law enforcement and policing and transportation," Open The Books CEO Adam Andrzejewski told The Daily Caller News Foundation. "Ultimately, the courts will determine the scope of federal funding penalties."

_{(Map: Open The Books)}

Trump signed an executive order Jan. 25 that denied federal funding to jurisdictions refusing to cooperate with federal officials seeking to deport illegal immigrants.

"Mayors defending their sanctuary city status by refusing to comply with federal law are essentially imposing a defiance tax on local residents," Andrzejewski said. "On average, this tax amounts to $500 per man, woman and child."

"Washington, D.C. municipal government received the highest amount of federal funding on a per capita basis," according to the report, with $3,228 per person, or nearly $2.1 billion total. Chicago "received the second highest amount of federal funding on a per capita basis," at $1,942 per person or $5.3 billion total.

Nearly $16 billion "in federal funds flowed into just 12 major American cities – where 1-in-5 illegal entrants" resided in 2016, the report said. Those twelve cities account for 2.2 million of the 11 million illegal immigrant population.

Those 12 cities, in order of the largest illegal immigrant population to smallest, are: Los Angeles; New York City; Chicago; Seattle; Austin, Texas; Newark, N.J.; Denver; Philadelphia; Minneapolis; San Francisco; Portland, Ore.; and Providence, R.I..

There are over 300 sanctuary governments in the U.S., according to a May, 2016, Department of Justice memo. Open The Books only examined the 106 cities.