Trump, who said the measures go into effect immediately, has yet to actually deploy the American military to any states as of yet.
Whether he can do so legally as a means to quell protests and whether such demonstrations constitute acts of terrorism, however, also remains to be seen.
The American Civil War-era Posse Comitatus Act prohibits federal troops from executing domestic law enforcement measures such as making arrests or searching people.
The president can, however, invoke the Insurrection Act in extreme cases.
The act — also from the 1800s — could essentially allow the deployment of active-duty military personnel or National Guard members in a state for use in law enforcement.
During his address, Trump urged mayors and governors to establish an “overwhelming law enforcement presence until the violence has been quelled.”
“A number of state and local governments have failed to take necessary action to safeguard their residents,” he said.
“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.”
Trump said his administration was already in the process of dispatching “thousands and thousands of heavily armed soldiers, military personnel and law enforcement officers” to put an end to the protests.
He added that a 7 p.m. curfew would be “strictly enforced” within Washington D.C. as well, promising lengthy jail sentences and severe criminal penalties for anyone caught breaking the law.
According to The Associated Press, between 600 and 800 National Guard members from five states were now being sent to assist the U.S. capital, citing senior defence officials.
Trump also criticized Antifa, lumping the left-leaning, anti-fascist movement together with other “organizers of this terror” he claimed were “leading investigators” of the violence unfolding across the U.S.
On Sunday, Trump declared that he would be classifying Antifa as a terrorist organization.
Currently, the U.S. does not have any laws in place to designate domestic groups as a terrorist entities — only foreign organizations could be classified as such.
Just minutes before Trump began speaking at the White House Rose Garden, National Guard members and police aggressively forced back peaceful protesters that were gathered in Lafayette Park.
Loud noises heard in the background prior to Trump’s address seemed to be those of police helicopters and the firing of tear gas or flashbangs.
After finishing his remarks, Trump later emerged from the front gates and walked through the park — which had been cleared of demonstrators — to St. John’s Church.
He later posed for photos — Bible in hand — alongside a group of advisers.
Earlier on Monday, Trump had mocked the nation’s governors as “weak,” demanding that they enforce tougher crackdowns and more arrests in their states amid another night of violent protest in several American cities.
“Most of you are weak,” Trump said, according to some of the local leaders. “You have to arrest people.”
Trump, who spoke to the governors on video teleconference alongside a handful of law enforcement and national security officials, said that they would “have to get much tougher.”
The protests, which were sparked by the killing of George Floyd — a Black man who died after being suffocated by a white Minneapolis police officer — have now entered their second week.
Several of the peaceful demonstrations have turned violent in many U.S. cities, with looters and rioters taking advantage of the chaos.
— With files from The Associated Press