The warning came amid reports of armed militias.
Deposed Venezuelan President Nicolás Maduro and his wife appeared in a federal court in New York City on Monday, following their capture by U.S. forces over the weekend in a military operation in the Venezuelan capital of Caracas.
Following the operation, President Donald Trump said that the U.S. would "run" Venezuela for an unspecified "period of time."
Venezuelan Vice President Delcy Rodriguez has been sworn in as interim leader to lead the country after what the Venezuelan Supreme Court described as Maduro's "kidnapping."
Ousted Venezuelan President Nicolas Maduro will appear in Manhattan federal court on Monday for arraignment on a four-count indictment that will charge him with allegedly leading a 25-year narco-terrorism conspiracy.
-ABC News' Aaron Katersky
Secretary of State Marco Rubio said Sunday the U.S. was in charge of "the direction" of the situation in Venezuela after U.S. forces arrested and deposed Venezuelan President Nicolás Maduro.
"President Trump was pretty clear yesterday. He said the United States is going to run Venezuela. Under what legal authority?" ABC News' "This Week" anchor George Stephanopoulos asked.
"Well, first of all, what's going to happen here is that we have a quarantine on their oil. That means their economy will not be able to move forward until the conditions that are in the national interest of the United States and the interests of the Venezuelan people are met," Rubio said.
But pressed on whether the U.S. was in charge of the country right now, Rubio said that what the U.S. was "running" was the direction of the situation.
"What we are running is the direction that this is going to move moving forward. And that is we have leverage," Rubio said.
"The leverage that we have here is the leverage of the quarantine. So that is a Department of War operation conducting, in some cases, law enforcement functions with the Coast Guard on the seizure of these boats," Rubio said.
Rubio added that Maduro was someone the U.S. "simply couldn't work with," and said that the administration was not recognizing Venezuelan Vice President Delcy Rodríguez as the current legitimate leader.
"We don't believe that this regime in place is legitimate via an election," Rubio said.
"Ultimately, legitimacy for their system of government will come about through a period of transition and real elections, which they have not had," he added.
-ABC News Nicholas Kerr
The Venezuelan Supreme Court on Saturday announced an order directing Delcy Rodriguez, the vice president, to assume the role of acting president.
The order cited the "exceptional situation created by the kidnapping of Nicolás Maduro Moros, President of the Republic, which constitutes a case of material and temporary impossibility for the exercise of his duties."
Under the order, which was posted in Spanish on the court’s official website, Rodriguez would in her temporary position have “all the powers, duties, and faculties inherent to the office of President of the Bolivarian Republic of Venezuela, in order to guarantee administrative continuity and the comprehensive defense of the Nation."
-ABC News' Victoria Beaule
Photos obtained by ABC News show a handcuffed Nicolas Maduro being escorted by Drug Enforcement Administrator Terry Cole and other federal agents after landing in New York on Saturday.
After arriving at Stewart Air National Guard Base in Newburgh, New York, Maduro was taken by helicopter to New York City and then to the Metropolitan Detention Center in Brooklyn.
Maduro, who was captured in Venezuela early Saturday morning along with his wife Cilia Flores, is facing federal narco-terrorism charges in the U.S.
