Boston Mayor Marty Walsh joined an escalating confrontation between the mayors of Democrat-led cities and President Donald Trump on Tuesday, warning that federal law enforcement agents won't be welcome in his city if the president decides to deploy them.

"We've seen the footage of unidentified federal officers aggressively detaining protesters in Portland, Oregon," Walsh said during a press conference Tuesday. "We've heard the president say he's bringing that strategy to Chicago and other cities.

"I want to express my support for Mayor [Edward] Wheeler of Portland and Mayor [Lori] Lightfoot of Chicago," Walsh added. "They've made it very clear that these federal actions were not needed or wanted or invited into their cities. And while we have no information that Boston is being targeted, I want to make absolutely clear: That behavior, and that type of so-called help, is not welcome here in the city of Boston."

Walsh went on to say that the federal government has been deploying personnel unilaterally, without consulting local officials — and that, rather than easing tensions, that approach is endangering protesters and escalating unrest. At one point, he called the strategy a "political ploy by the president."

Consequently, Walsh said, he's joining Wheeler and Lightfoot — and the mayors of Atlanta, Seattle, Kansas City, and Washington, D.C. — in signing aletter asking the Departments of Justice and Homeland Security to withdraw their personnel immediately. In addition, Walsh and the other mayors areurging Congress to hold public hearings on the issue.

"In Boston, we support the movement for racial justice," Walsh said. " We've built trust and solidarity with those who are demonstrating. And in Boston, demonstrators, with very few exceptions, have been peaceful.

"The people out marching are calling for the most fundamental right our country was founded on," he added. "And the Boston Police Department has certainly preserved public safety while protecting the rights of free speech and free movement. Unfortunately, this seems to be another situation where the president ... doesn't understand or believe in those rights."