WASHINGTON — The Department of Homeland Security started an effort a year ago this month to address domestic terrorism, white nationalist threats and other acts of homegrown violence, a major shift for an agency created after the Sept. 11, 2001, attacks to protect the country from foreign terrorism.

Today the plan to carry out that new mission remains stalled in a bureaucratic morass as clashes between protesters and counterprotesters have escalated to precisely the violent acts that the plan was supposed to address.

Instead, a new crop of Department of Homeland Security leaders, led by the confrontational acting secretary, Chad F. Wolf, appear to be doing the opposite of what had been promised. Far from cooperating with local governments and citizens to combat domestic unrest, particularly from the far right, they have joined President Trump in lashing out at American mayors and governors while deploying federal tactical teams to cities — often expressly against the wishes of the local governments with which they had pledged to cooperate.

On Monday night on Fox News, Mr. Wolf said he spoke with Attorney General William P. Barr about arresting leaders of the Black Lives Matter movement.

Killings this summer in Portland, Ore., Oakland, Calif., and Kenosha, Wis., have heightened fears that the kind of ideological extremism that the department sought to address last September has burst onto the streets of the nation’s cities.

The document published a year ago singled out white supremacist and anti-government extremism as primary national security threats, while also noting the potential threat posed by Antifa, a loose-knit anti-fascist movement. Officials at the time committed to releasing a detailed implementation plan within months. That blueprint was to guide federal and local governments as well as community stakeholders in how to work cooperatively to identify threats and address politically motivated violence.

“It’s government dysfunction and bureaucracy at its worst,” said Daryl Johnson, a former senior analyst for the Department of Homeland Security whose 2009 report warning of the rise of right-wing extremism was withdrawn after it prompted political backlash from conservative leaders furious that it suggested some military veterans were joining far-right movements.

Some city leaders and former department officials went further, saying that in the absence of cooperation, the president was exploiting the unrest for his re-election campaign, singling out left-wing agitators while ignoring white supremacists and right-wing groups.

Elizabeth Neumann, a Trump appointee who left the department in April after serving as an assistant secretary for counterterrorism and threat prevention, said some White House officials had even sought to suppress the phrase “domestic terrorism.”

The administration criticizes Antifa, even though the department considers it to be a “low grade” menace, she said, but it appears unwilling “to come out and repeatedly and consistently criticize the white supremacist global threat,” which is far more lethal.

“It’s clear by labeling Antifa domestic terrorists, they’re just doing this for political purposes,” she said.

Ms. Neumann said that in the weeks before her departure, she pushed the domestic extremism implementation plan through the department’s bureaucracy to its policy office. The plan was to guide local governments on how to spend new grant funding that the agency secured last year from Congress, while setting a timeline for various law enforcement and government officials to meet on the emerging threats. It also instructed the department on how to collaborate with local leaders to identify community members, like social service providers and mental health professionals, who could help intervene before someone engaged in an attack.

The department planned to pair the blueprint with a new assessment of the threat posed by people affiliated with extremist groups, former department officials said. Both reports are caught in the department’s protracted review process.

As the plan languishes, the Trump administration has sought confrontation rather than collaboration. Mr. Wolf has said he does not need the permission of local leaders to deploy tactical teams from Immigration and Customs Enforcement or the Border Patrol to American cities, and on Sunday he left open the possibility of sending more agents to Portland.

The Department of Homeland Security did not respond to requests for comment.

ImageOn Monday night on Fox News, Chad F. Wolf, the acting homeland security secretary, said he had spoken with Attorney General William P. Barr about arresting leaders of the Black Lives Matter movement.
Credit…Al Drago for The New York Times

After the Portland mayor, Ted Wheeler, pleaded with the federal government to work with his office to quell the unrest in the city, Mr. Trump called him a “dummy” and indicated more federal agents would soon be on the way.

Mr. Wolf has said that he had offered assistance to the local government in Portland but was rejected. He wrote a letter to Mr. Wheeler on Monday asking him to request assistance from his agency.

“At the same time, President Trump has made it abundantly clear that there will come a point when state and local officials fail to protect citizens from violence,” Mr. Wolf said in the letter, adding that “the federal government will have no choice but to protect our American citizens.”

On Monday, Mr. Trump defended the caravan of Trump supporters who drove into Portland over the weekend as “peaceful protesters,” even though video captured some of them shooting paintball guns from pickup trucks as protesters threw objects at them.

The victim of a fatal shooting during those protests was wearing a hat with the insignia of Patriot Prayer, a far-right group based in Oregon. A Department of Homeland Security intelligence briefing from July had warned law enforcement agencies that previous Patriot Prayer events had attracted white supremacists and devolved into violent clashes with anarchists. While the White House has blamed Antifa for the shooting, no suspects have been arrested.

Mr. Trump also defended as self-defense the lethal actions of Kyle Rittenhouse, a 17-year-old Illinois resident who has been charged with fatally shooting two people during a demonstration over the police shooting of Jacob Blake. Before the shooting, Mr. Rittenhouse had stood alongside armed militia members.

“I guess he was in very big trouble,” Mr. Trump said. “He probably would have been killed. But it is under investigation.”

Trump supporters are organizing another event in Portland for the coming weekend. Outside the city, one national antigovernment group has called for open civil war, saying that if the president did not intervene in Portland, the militia would.

In the meantime, the F.B.I. has opened over 300 domestic terrorism investigations since May 28, when demonstrations erupted around the country in response to the killing of George Floyd.

“As our citizens have organized lawful demonstrations across this country following the tragic events in Minneapolis, anarchists have continued to exploit this lawful First Amendment activity as a shield for their violent behavior,” Erin Nealy Cox, the U.S. attorney in the Northern District of Texas, testified in August at a Senate Judiciary Committee hearing on preventing violent protests.

Ms. Cox was appointed by Mr. Barr to lead a Justice Department task force on violent anti-government extremists, including those that identify with Antifa or the far-right “boogaloo” movement, whose goal is to incite a race war in the United States.

“Somehow, the notion of committing violence in the name of an anti-government dogma — be it Antifa, boogaloo or any of the other espoused ideologies — has been gaining traction at an alarming rate,” Ms. Cox said.

The delay of the release of the Department of Homeland Security’s plan is consistent with the Trump administration’s underplaying of violence perpetuated by right-wing extremist groups, which have proliferated in the past three and a half years. Under Mr. Trump, the department’s office tasked with paying out grants and coordinating with local police departments to prevent domestic threats has shriveled in size and has been renamed numerous times.

The strategy framework released by the department last September identified numerous rising threats, including white supremacist groups and anti-government extremists, like the boogaloo movement. The Air Force sergeant charged with killing a federal security officer outside a courthouse in Oakland, Calif., expressed allegiance to the movement and said he used the protests against racial injustice as a cover to attack law enforcement.

“The administration coming out and naming one group terrorists and not saying anything about white nationalism? It’s ridiculous,” said Mr. Johnson, whose 2009 report warned that economic dislocation and the recent election of a Black president could fuel right-wing extremism. “It comes at a cost to the people who live in these communities who are affected by the violence.”

Katie Benner contributed reporting.