Washington-President Donald Trump vowed Monday to order a military crackdown on once-in-a-generation violent protests gripping the United States, saying he was sending thousands of troops onto the streets of the capital and threatening to deploy soldiers to states unable to regain control.

The dramatic escalation came a week after the death in Minneapolis of George Floyd, an unarmed black man who was killed when a white police officer knelt on his neck, leading to the worst civil unrest in decades in New York, Los Angeles and dozens of other American cities.

After being criticized for his silence on the worsening crisis, Trump struck a martial tone in a nationwide address from the White House garden, as police fired tear gas on peaceful protesters outside the fence.

“I am dispatching thousands and thousands of heavily armed soldiers, military personnel and law enforcement officers to stop the rioting, looting, vandalism, assaults and the wanton destruction of property,” Trump said.

He slammed the previous night’s unrest in Washington as a “total disgrace” and called on governors to “dominate the streets.”

“If a city or state refuses to take the actions that are necessary to defend the life and property of their residents, then I will deploy the United States military and quickly solve the problem for them,” he said, denouncing “acts of domestic terror.”

Despite the president’s rhetoric, Monday’s protests appeared largely peaceful in major cities, though some looting was reported in New York and Los Angeles.

During his address, however, law enforcement including military police used tear gas to clear protesters outside the White House so the president could walk across the street to the two-centuries-old St Johns church, hit with graffiti and partially damaged by fire during unrest on Sunday.

“We have a great country,” Trump declared as he stood before the church’s boarded up windows, held up a Bible and posed for photographs.

The backlash was swift.

“He’s using the American military against the American people,” tweeted Democratic presidential hopeful Joe Biden.

“He tear-gassed peaceful protesters and fired rubber bullets. For a photo. For our children, for the very soul of our country, we must defeat him,” he said.

Washington’s Episcopalian bishop, Marian Budde, said she was “outraged” at the church visit, which she said Trump did not have permission for.

Thousands of people have participated in the nationwide demonstrations against police brutality and racism since Floyd’s killing.

It was the most widespread unrest in the United States since 1968, when cities went up in flames over the slaying of civil rights icon Martin Luther King Jr.

Many of the demonstrations have been peaceful and marked by moments of catharsis such as officers hugging tearful protesters and marching or kneeling alongside them.