President Donald Trump’s campaign accused Minneapolis mayor Jacob Frey on Monday of trying to block the president’s scheduled political rally in the city.

“This is an outrageous abuse of power by a liberal mayor trying to deny the rights of his own city’s residents just because he hates the President,” Trump campaign manager Brad Parscale said in a statement sent to reporters.

The Trump campaign revealed that Frey was trying to tack on a $530,000 security fee and other costs to the Target Center for the scheduled event on Thursday. The Target Center’s management, AEG Management TWN, tried to pass on the fees to the Trump campaign, threatening to block them from using the arena if they did not pay.

But the campaign threatened to sue the Target Center for a breach in contract, noting that Secret Service was in charge of security.

“This last-minute squeeze seems to be nothing but a pretextual political effort with serious First Amendment ramifications,” a letter read from the Trump campaign’s lawyer to the Target Center’s management firm.

Frey protested the news that Trump was planning to rally in Minneapolis.

“While there is no legal mechanism to prevent the president from visiting, his message of hatred will never be welcome in Minneapolis,” Frey said in a statement in September.

The campaign noted that the Target Center arena’s sudden security fees were extraordinarily high.

In 2009, President Barack Obama rallied at the Target Center, which led to an estimated $20,000 cost for additional security from the police chief, according to a report at the time.

“The Campaign cannot be in breach of an obligation it does not owe to AEG,” the letter continues. “Yet AEG’s failure to deliver the Target Center on October 9 would be a breach of contract.”

The mayor’s attempt to shut down a political event with high security fees is a tried and true tactic of the left.

The Trump campaign sent the letter Monday night as Frey was attending a playoff baseball game between the Minnesota Twins and the New York Yankees.

The rally is scheduled for Thursday night.