Boston Mayor Michelle Wu is urging owners of parking lots and garages to reject federal immigration officials’ requests to rent spots for their vehicles.

In a letter released Tuesday, Wu said, “Were ICE to procure such resources, it would constitute an unprovoked and unwarranted escalation, creating potentially significant risks to public safety and halting economic activity across our entire region.”

Earlier this month, ICE posted a public notice seeking nearly 250 parking spots around Boston, stoking fears of escalated ICE enforcement in the city. It was part of a wider federal push to conduct “market research” and locate “Surge Parking” in 14 communities across the country.

The Wu letter culminates in a plea: “Today, I ask you to join us: Reject any proposition by ICE to facilitate an attack on the people of Boston. In the face of escalating attacks on cities across the country, we have repeatedly seen that the strongest defense is solidarity.”

The city also has sent a Freedom of Information Act request to the federal government to learn of any responses from lot owners to ICE’s request.

In a post on X, Department of Homeland Security officials called Wu’s actions “unhinged.” It said, “She knows she has NO authority to block us from using private property.”

Earlier this year, Wu and the leaders of six other cities and towns signed orders banning federal agents from making arrests and taking action on city property — which includes some parking lots. But she has acknowledged that when it comes to private property, the city has fewer options.

“We will have to look into full legislative and legal options,” she told reporters.

ICE’s local headquarters is in Burlington, Mass.

When news broke that ICE is looking to expand its parking presence in Boston, Gov. Maura Healey pushed back, saying the agency “absolutely cannot” be enabled to “ramp up” deportation efforts in Massachusetts.

The governor also signed the PROTECT Act into law earlier this month, which seeks to restrict warrantless ICE arrests in courthouses, public schools, childcare centers and healthcare facilities.

ICE surges in some U.S. cities have had fatal consequences. Federal agents have shot and killed people in Biddeford, Maine, Houston and Minneapolis, intensifying public opposition to immigration enforcement.