Boston Mayor Marty Walsh vowed to protect the city's undocumented immigrant population from President Donald Trump in a rousing speech Wednesday where he said he was "deeply disturbed" by the White House's new anti-immigrant stance. 

Trump ordered Wednesday the construction of a wall along the U.S.-Mexico border. He also said he would stop funding for sanctuary cities that do not help federal authorities detain undocumented immigrants.

"The day is over when they can stay in our country and wreak havoc," Trump said, referring to undocumented immigrants.

Walsh responded by calling Trump's policies destructive. Roughly 28 percent of Boston's residents are foreign born and 48 percent have at least one parent who is an immigrant.

“We will not back down from our values that make us who we are as a city,” Walsh said during a press conference. “We will fight for our residents, whether immigrant or not, and provide the best quality of life for all Bostonians. I will use all my power within lawful means to protect all Boston residents, even if that means using City Hall itself as a last resort.”

Walsh said residents fearful of the Trump administration could even seek shelter at Boston City Hall.

"I will never turn my back on those who are seeking a better life," Walsh said. "We will not be intimidated by the threat to federal funding. We have each other's backs, and we have the Constitution of the United States of America on our side."

He later tweeted: "We are a city & nation built on immigrants and we depend on newcomers to maintain the vitality of our country."

City officials lit up City Hall Wednesday night in patriotic colors to help spread the message. "City Hall is red, white and blue tonight. ALL are welcome here," tweeted Daniel Koh, Walsh’s chief of staff.

Walsh, a Democrat, was elected as mayor in 2014.