PORTLAND, Ore. — A top Homeland Security official on Sunday said the agency will maintain a heavy presence in Portland — and send reinforcements to other U.S. cities if violence surged — as the mayor of Oregon's largest city implored federal agents to stand down amid escalating clashes with protesters.

Kenneth Cuccinelli, acting deputy secretary of the Department of Homeland Security, said the agency had deployed tactical units from U.S. Immigration and Customs Enforcement and U.S. Customs and Border Protection to help defend federal buildings and officers in the Pacific Northwest city. He said DHS had expanded its numbers in other cities as well, including Washington, D.C., as demonstrations escalated in recent months.

“You can expect that if violence continues in other parts of the country, the president has made no secret of the fact that he expects us where we can cooperate or have jurisdiction to step forward and expand our policing efforts there to bring down the level of violence,” Cuccinelli said in an interview Sunday.

DHS and Justice Department personnel have made about two dozen arrests since July 4 in the vicinity of the federal courthouse in Portland, not including short-term detentions of suspects whom agents want to question, according to a DHS official who spoke on the condition of anonymity because they were not authorized to discuss federal law enforcement operations in Portland. The protesters’ use of black clothing, face coverings and diversion tactics have made it difficult for federal agents to identify suspects, they said.

DHS teams were deployed to reinforce the Federal Protective Service in Seattle, as well, before July 4 in anticipation of major disturbances, but the Seattle team has been withdrawn, the official added.

While the DHS official said there are no immediate plans to increase the presence in other cities, the president of Chicago’s police union on Saturday published a public letter to President Trump asking for federal assistance in controlling the “chaos” in city. Union President John Catanzara also criticized Mayor Lori Lightfoot, whose office called the letter “a stunt,” in a statement to CBS.

Portland Mayor Ted Wheeler on Sunday implored the “dozens, if not hundreds” of federal agents to leave the city, saying that unidentified Homeland Security officers were detaining residents in unmarked minivans.

“Their presence is neither wanted nor is it helpful and we’re asking them to leave,“ Wheeler (D) said. “In fact, we’re demanding that they leave.”

In response, Cuccinelli said, “We don’t have any plans to do that.”

“When the violence recedes, then that is when we would look at that,” he said. “This isn’t intended to be a permanent arrangement, but it will last as long as the violence demands additional support to contend with.”

Cuccinelli said the agency isn’t naming the federal officers to protect them and their families from doxing and other harassment, but he said they are wearing patches identifying their agencies and numbers that can be traced to them in case someone wishes to file a complaint.

Portland has had protests since the May 25 killing of George Floyd and has been scarred with graffiti, burned buildings and boarded-up shops. City officials — who are also contending with the novel coronavirus — say the Trump administration is antagonizing protesters, violating their rights and interfering with local efforts to quell the demonstrations. But federal officials say they are defending their federal officers and institutions in a city that cannot keep them safe.

Portland Police Association President Daryl Turner on Sunday asked for a moratorium on violence by protesters. He would not, however, say whether he supported or opposed federal presence in Portland. “Our city is under siege by rioters,” he said. “This is no longer about George Floyd, this is no longer about racial equity or social justice ... this is about violence, destruction, chaos and anarchy.”

He asked to sit down with stakeholders to “evolve policing to what our communities want us to be,” yet said that can’t happen with the agency spread thin by the ongoing unrest from protests.

In an interview Sunday, Wheeler said he thought that the ongoing protests after Floyd’s killing in Minneapolis police custody had settled into a calmer rhythm and the vandalism had subsided before federal agents arrived. But now, after multiple days of violent skirmishes between protesters and agents deployed by DHS, the mayor said, he worries someone could be killed.

Multiple videos and personal accounts have surfaced in recent days of CBP agents in military-style gear descending on demonstrators, including Mark Pettibone, 29, as he walked home from a protest. He said he was taken away in an unmarked van.

Portland resident Christopher David said he attended his first protest Saturday evening after reading about the tactics used by federal officials, hoping to have a conversation with the officers. He wore a sweatshirt, hat and backpack that he thought clearly indicated he was a Navy veteran.

“I wanted to give them pause. I was hoping they would respect that long enough so that we could talk,” said David, 53. “I wanted to ask them why they weren’t honoring their oath to the Constitution. But that was overall a stupid idea, there was no talking.”

David had watched as protesters dismantled fencing and placed pieces in front of doorways, but hadn’t participated himself. When federal officers made an appearance just around 11 p.m., David tried to ask them questions, he said, but a federal officer dressed in camouflage swung a baton at him multiple times. David didn’t react until another officer sprayed him in the face with pepper spray.

“Their response was absurd,” he said. “They started out wanting to dominate and that’s exactly what they tried to do. There was no compromise, no de-escalation. They almost behaved like a mob. After a while, you didn’t know whether they were the proud boys or whether they were federal officers.”

David suffered multiple bruises and a broken hand.

Oregon Attorney General Ellen Rosenblum filed a federal lawsuit against Homeland Security and its subagencies Friday alleging the federal government had violated Oregonians’ civil rights by seizing and detaining them without probable cause during protests against police brutality in the past week.

“If the federal government continues to ratchet up its incendiary rhetoric and if federal troops continue their unconstitutional occupation of our city, it could lead to someone being killed. Either a demonstrator or a local or state law enforcement official,” Wheeler told The Washington Post. “If either case happens, there’s no telling how the community might react.”

But Wheeler’s and the police union’s statements in early July show that the city had been facing violent threats before DHS says it ramped up its presence.

On July 3, Wheeler called for the “nightly violence” to end.

“This has been going on for more than a month now,” Wheeler tweeted July 3, saying that groups were targeting the Justice Center and “threatening the safety of hundreds of inmates and employees inside.”

“They continue to hurt small businesses owned by people of color, instill fear in communities of color, and start fires in buildings with people inside, in one specific case, even bolting emergency doors so that they could not escape,” he said in a tweet.

The Portland police union, whose union hall was broken into and burned over the weekend, posted online July 8 that the union’s executive board had “no confidence” that the City Council would stop the violence. Union officials said officers had “endured weeks of rocks, bricks, bottles, mortars, and other objects hurled at them with hate.”

“Enough,” the union said in a Facebook post.

Although Cuccinelli declined to provide the number of federal agents in Portland, he said it was “somewhere in between” the “dozens” or “hundreds” cited by Wheeler.

Cuccinelli said DHS deployed a number of federal agents to supplement the Federal Protective Service, which guards federal buildings such as courthouses, over the Fourth of July weekend amid growing intelligence that demonstrators were targeting federal buildings. A federal protective officer in Oakland, Calif., was shot and killed in May, allegedly by an Air Force sergeant seizing on the protests to sow mayhem.

He said the deployment took place five weeks into the violence in Portland: “So for anyone to say that our arrival 30 or so days into daily violence in their city was caused by something that showed up later is just illogical and silly.”

“We had intelligence that the federal facilities were going to be further targeted, so we deemed it unsafe for the FPS forces available by themselves,” Cuccinelli said.

He said the reinforcements were highly trained officers from Immigration and Customs Enforcement’s investigative division; Homeland Security Investigations, which probes crimes such as drug and human trafficking; and Customs and Border Protection’s BORTAC tactical unit. He said they were deployed “substantially” over the July 4 weekend — several weeks into the protests — as it became clear that Portland authorities were not tamping down the violence.

He said the FPS is in charge on the ground, and the CBP and ICE support teams are reporting to them. He also discounted a New York Times report that an internal DHS memo said the teams were not trained for mass demonstrations or riot control. And he said they were operating with full authority under the law.

“All of the people in Portland are trained for the mission,” he said. “All the officers present have crowd control training.”

House Democrats on the Judiciary, Homeland Security, and Oversight and Reform Committees condemned the use of “violent tactics against peaceful protesters in Washington, D.C., Portland and elsewhere across the country, and they sent letters to the Justice Department and DHS inspectors general calling for an inquiry.

“The legal basis for this use of force has never been explained — and, frankly, it is not at all clear that the Attorney General and the Acting Secretary are authorized to deploy federal law enforcement officers in this manner,” they wrote, saying the attorney general “does not have unfettered authority to direct thousands of federal law enforcement personnel to arrest and detain American citizens exercising their First Amendment rights.”

Wheeler hadn’t been told federal forces would descend on his city, he said, until after the officers were already there and said he was never asked whether Portland wanted the federal government’s help.

And to top it off, he said, the federal forces hadn’t helped to clean up any of the property damage that acting DHS secretary Chad Wolf seemingly used as justification for sending federal forces in to deal with “violent extremists.”

“It’s totally disingenuous,” Wheeler said. “What we needed were people who were trained in de-escalation, containment strategy, targeted arrests of individuals who are actually engaged in illegal activity. Instead what they’ve given us is warfare on our streets.”

Nick Miroff contributed to this report.