U.S. President Donald Trump's attempt to strip municipalities of federal dollars for shielding illegal immigrants threatens $2.27 billion in annual funds for the nation's 10 largest cities, a Reuters analysis of federal grants found.

Trump plans to make good on his campaign pledge to block federal funding to states and cities where local law enforcement refuse to report undocumented immigrants they encounter to federal authorities, White House press secretary Sean Spicer said.

"The American people are no longer going to have to be forced to subsidize this disregard for our laws," Spicer said.

Spicer said an executive order signed by Trump on Wednesday directs the Secretary of Homeland Security to look at federal funding to cities to figure out "how we can defund those streams."

Mayors and city councils of those cities have said that they will not be pressured to report illegal immigrants to federal agents.

(For a graphic of risks to sanctuary cities, see: tmsnrt.rs/2jSYT4I )

While Trump has the authority to cut some kinds of funding to the cities, cuts to other federal funding would require an act of Congress.

Reuters analyzed federal grant records to tally the estimated federal funding at risk among the 10 largest cities which totaled an estimated $2.27 billion.

The total amount remains unclear, as federal money can be filtered through state governments or granted directly to social-service organizations or other groups.

The numbers do not include federal money for law enforcement, which was excluded in the executive order, and programs like Medicaid, which are administered by state governments.

Though details remain vague, the order could jeopardize billions of dollars in housing, health, education and other types of federal aid.

Among the funds at risk are $460 million that the federal government gave out to fund Head Start pre-school programs in the 10 largest 'sanctuary cities' in the most recent fiscal year, the analysis found.

Washington also sent $238 million to municipalities to fund airport improvements and $153 million for HIV prevention and relief.

Local governments in Los Angeles County, for example, received $582 million in federal aid in the most recent fiscal year. That aid included $207 million for the Head Start preschool program, $70 million last year for airport improvements, and $114 million for community development funds used for housing and other needs.

New York Mayor Bill de Blasio, on Tuesday, said he is going to put an additional $250 million a year away in reserves for four years because of a "huge amount of uncertainty" emanating from Washington.

If the Trump administration actually moved to cut funding, "we would be in court immediately to stop it," de Blasio told reporters.

Chicago Mayor Rahm Emanuel reiterated the city would remain a sanctuary for undocumented immigrants. In December he pledged $1 million to assist immigrant families.

NOT AN OFFICIAL DESIGNATION

Sanctuary city is not an official designation.

Boston, Denver, Los Angeles, and Seattle have not declared themselves so-called sanctuary cities. But each city has vowed some sort of protection to undocumented residents.

Boston's city council in 2014 directed local law enforcement not to detain individuals based on immigration status except in cases where there is a criminal warrant. Boston expects to receive approximately $65.5 million in federal revenue this year.

Boston Mayor Marty Walsh said in a statement on Wednesday he was "deeply disturbed" by the Trump's actions.

"I will use all of my power within lawful means to protect all Boston residents - even if that means using City Hall itself as a last resort," he said.

Denver, too, does not have a formal policy of non-cooperation with the federal government on immigration enforcement, but the city does not support "unlawful detention in our jails," said Mayor Michael Hancock. Denver received about $39 million in federal funds in fiscal 2016.

Trump's plans to spur job growth and boost the economy would likely be harmed by federal funding cuts in many cities. Many public workers' salaries could be in jeopardy as well as the facilities and institutions that keep American trade moving, such as ports.

Seattle received approximately $72.7 million of federal dollars in fiscal year 2016. If the Port of Seattle were to shutter from a lack of federal funding, "that's going to impact the economy and trade in a really big way," said Kevin Schofield of Seattle City Council Insight, an independent website focused on the city issues.

"(Trump) has vastly overstated the funding that could be at issue with these sanctuary policies. Any attempts to withhold funds will certainly be the source of litigation and the courts, not the president, will be the ultimate arbitrator," said Peter Markowitz, a professor at New York's Cardozo School of Law, who focuses on immigration. - { Reuters}