The Trump administration is sending its strongest signals yet that Denver is about to be labeled a sanctuary city and lose federal funding.

There's no official definition of sanctuary city, but the criteria laid out Tuesday by the Attorney General Jeff Sessions and the Justice Department would block Denver from getting about $425,000 a year.

Denver got about $3 million in funding under one particular grant program, the Edward Byrne Memorial Justice Assistance grants, since 2010. That program provides money for crime-fighting on the state and local levels.

The new guidelines announced on Thursday hinge on how the Denver Sheriff's office handles prisoners who are wanted for deportation. The feds will strip funding from cities that don't allow immigration agents into jails to question inmates. The Denver jail turns away ICE agents unless they have a warrant.

The Justice Department will also label a city a sanctuary city if it doesn't provide 48 hours notice before releasing someone that ICE wants to take into custody. The Denver Sheriff's Department and immigration agents have disagreed recently about short notice given before inmates are released.

The announcement does not say that local jails should an inmate for the feds.

In the statement, Sessions said:

"So-called 'sanctuary' policies make all of us less safe because they intentionally undermine our laws and protect illegal aliens who have committed crimes. These policies also encourage illegal immigration and even human trafficking by perpetuating the lie that in certain cities, illegal aliens can live outside the law..."

Denver has never formally called itself as a sanctuary city, but it has long said it has the law on its side despite already challenging some federal rules, and these new rules could mean new lawsuits.

RELATED: A formal proposal to keep Denver out of immigration enforcement

RELATED: This is why Trump's threat to de-fund sanctuary cities doesn't apply to Denver