DENVER (KDVR) — The city and county of Denver is suing the Trump administration alongside Chicago, Boston, San Francisco and Seattle, after funding for a counterterrorism program was frozen.

The grant program is called Securing the Cities, and Denver said Monday that the funding has been used for equipment used daily by the Denver police, Denver Fire Department, Denver Health and the Colorado State Patrol. It also funds security sweeps and infrastructure monitoring at Red Rocks concerts, sports games and parades.

“National security is not a Democratic or Republican issue. It’s an American one, and losing this funding makes America less safe,” said Mayor Mike Johnston in a city release Monday. “You wouldn’t think we would need to go to federal court to explain why it’s important to protect citizens from terrorism, but here we are.”

This is Denver's third lawsuit against the Trump administration. Earlier this month, a judge issued a preliminary injunction in favor of Denver after the Trump administration threatened to withhold funding for transportation programs.

On Monday, Denver said the Securing the Cities funding was used to conduct security sweeps and monitor critical infrastructure during high-profile visits to Denver, such as President Joe Biden's visit to Denver in November 2023 or President Trump's October 2024 rally in Aurora.

"The Trump Administration has not provided reasoning for why the funding was paused," the city said in a release on Monday.

The city said it paused all "new expenditures" except staff wages since the U.S. Department of Homeland Security announced the funding freeze on May 14. Denver said this has led to cancellations of "critical" training and that repairs for equipment used to detect nuclear or radiological materials cannot be completed.

The lawsuit alleges that Denver also cannot pay the vendor providing software used to manage and track nuclear and radiological detection equipment, "forcing Denver to manually maintain records in Excel spreadsheets."

"It also means a mobile-security unit designed to monitor events for risks to public safety is sitting in storage instead of being used in the field," the city said.

In the lawsuit, the cities allege they have sent 11 requests since Feb. 21 for reimbursement of expenditures that DHS had previously approved.

"DHS has effectively ignored Plaintiffs' requests while holding open the possibility that DHS may someday reimburse Plaintiffs," the lawsuit states. "For example, on May 28, 2025, DHS stated that it would reimburse Chicago that day, but only if Chicago resubmitted previously provided information about its five reimbursement requests within ten minutes. Although Chicago provided the requested information that same day, DHS has not reimbursed Chicago as of the date of this filing."

The city said in a release on Monday that Denver is among 13 cities and counties named by DHS as having an elevated risk of terror attacks, mainly due to the city's high volume of special events, concentration of federal and military facilities, and position as a major transportation hub, both by ground and air.

The cities are asking the court to rule that the Trump administration violated the U.S Constitution's separation of powers, the Administrative Procedures Act and acted "ultra vires," or beyond its scope of powers, by freezing the funds. The cities are also asking for a preliminary and permanent injunction to prevent the administration from freezing the funds again.