In escalation of tensions, Trump recognizes Venezuela's opposition leader as head of government The opposition-controlled legislature recognized Juan Guaidó as acting leader.

As Venezuelans commemorated the 61st anniversary of an uprising that saw one of the country’s worst dictators dethroned, U.S. President Donald Trump declared Nicolas Maduro's presidency "illegitimate" on Wednesday and encouraged other Western Hemisphere countries to recognize opposition leader Juan Guaidó as interim president.

The announcement comes amid some measure of chaos in Venezuela, where people all over the country are taking to the streets to protest Maduro's presidency -- days after his second term in office began following elections that were criticized by Venezuelans and the international community as illegitimate.

In the Oval Office on Wednesday, Trump warned that his administration had "all options" on the table on how to further respond.

"We're not considering anything, but all options are on the table," Trump told reporters. "All options, always. All options are on the table."

Earlier in the day, the White House released a statement by him calling Venezuela's National Assembly "the only legitimate branch of government duly elected by the Venezuelan people."

"The people of Venezuela have courageously spoken out against Maduro and his regime and demanded freedom and the rule of law," the statement said. "We continue to hold the illegitimate Maduro regime directly responsible for any threats it may pose to the safety of the Venezualan people."

Maduro responded by breaking relations with the U.S. and ordering all American diplomats to leave the country within 72 hours. Given that the U.S. no longer recognizes Maduro's authority, it is unclear whether they would comply.

The State Department did not immediately respond to a request for comment, but a senior administration official told ABC News, "The order is meaningless." That could set up a standoff -- U.S. diplomats refusing to leave with Maduro's security forces aiming to push them out.

"Trust me on this one, if Maduro is stupid enough to test @realdonaldtrump by harming any U.S. diplomat, the consequences would be swift & severe," warned Sen. Marco Rubio, R-Florida, who met with Trump and other Florida lawmakers on Tuesday to discuss Venezuela.

For his part, Guaidó tweeted earlier that as the new acting president, he called on all U.S. diplomats to stay in the country and maintain diplomatic ties. He later tweeted his thanks to Trump, too, writing in Spanish, "On behalf of all Venezuela I thank you for your commitment to support the will of the Venezuelan people."

De parte de toda #Venezuela agradezco su compromiso de respaldar la voluntad del pueblo venezolano. https://t.co/umczpmkiWQ

About a dozen other countries followed the U.S. lead and also recognized Guaido as the new head of state, including a collection of Western Hemisphere countries known as the Lima Group that includes Canada, Chile, Brazil, Colombia, Argentina, and Peru. Mexico was the only member of the Lima Group not to sign a statement of support for Guaidó.

Since Maduro took power after Chavez’s death, Venezuela has experienced a rapid decline in what was already a struggling economy.

Venezuela has been undergoing an unprecedented crisis, with hyperinflation hitting 80,000 percent by the end of 2018, according to Forbes. Since 2014, more than three million people have left the country amid the deepening economic crisis, and food and medicine shortages continue, according to the United Nations.

We've barely scratched the surface of what actions the United States can take from an economic sanctions front. If they choose the route of violence and seek to usurp the constitutional order and democracy, let us be clear that we have a host of options and we will take every one of those options seriously..

Maduro’s reign has also been plagued by political oppression and crackdowns on activism and protest activity. More than 12,500 people have been arrested while attending a protest, according to Foro Penal, a Venezuelan human rights watchdog organization.

The U.S. has responded to that crackdown with increasingly-sharp sanctions -- even sanctioning Maduro himself. But a senior administration official warned Wednesday that there would be more pressure to come.

"We've barely scratched the surface of what actions the United States can take from an economic sanctions front," the official told reporters during a background briefing, adding, "If they choose the route of violence and seek to usurp the constitutional order and democracy, let us be clear that we have a host of options and we will take every one of those options seriously."

But the country’s opposition has been emboldened by Guaidó, the new president of the National Assembly who, with only six days in office, said he was ready to become acting president of the country until legitimate elections could be held. He also asked for military support to do so.

Nicolas Maduro is a dictator with no legitimate claim to power. He has never won the presidency in a free and fair election and has maintained his grip of power by imprisoning anyone who dares to oppose him.

Venezuela’s opposition has been broadcasting Wednesday's planned protests for weeks. In parts of the country, people took to the streets as early as Monday, leading to the arrest of 43 people in just 48 hours.

Alfredo Romero, executive director of Foro Penal, confirmed the arrests to ABC News, adding that some of those detained are injured.

While the crisis in Venezuela has spiraled into chaos in the last several months, Guaidó has emerged as a leader of the opposition after being elected president in December 2018.

The National Assembly voted to declare Maduro illegitimate and remove him from office this month, allowing Guaidó to be chosen as acting head of state.

In his own statement released on Wednesday, U.S. Secretary of State Mike Pompeo already brushed Maduro aside, saying the U.S. will now work with the "new" Venezuelan government on free and fair elections and possibly even to administer aid -- something Maduro has blocked the U.S. from doing.

"The Venezuelan people have suffered long enough under Nicolas Maduro’s disastrous dictatorship," Pompeo's statement said. "We call on Maduro to step aside in favor of a legitimate leader reflecting the will of the Venezuelan people.."

"We will work closely with the legitimately elected National Assembly to facilitate the transition of Venezuela back to democracy and the rule of law, consistent with the Inter-American Democratic Charter," he added, calling on the Venezuelan military and security forces "to support democracy and protect all Venezuelan citizens."

The Venezuelan people have suffered long enough under Nicolas Maduro’s disastrous dictatorship.

"The new Venezuelan government carries the flame of democracy on behalf of Venezuela. The United States pledges our continued support to President Guaidó, the National Assembly, and the Venezuelan people," Pompeo concluded.

Trump's and Pompeo's declarations come a day after Vice President Mike Pence made a similar statement, addressing the people of Venezuela through a video posted to Twitter.

“Nicolas Maduro is a dictator with no legitimate claim to power," Pence said in his address. "He has never won the presidency in a free and fair election and has maintained his grip of power by imprisoning anyone who dares to oppose him.”

“The United States joins with all freedom-loving nations in recognizing your National Assembly as the last vestige of democracy in your country, for it is the only body elected by you, the people,” Pence said.

“As such, the United States supports the courageous decision by Juan Guaidó, the President of the National Assembly, to assert that body’s constitutional powers, declare Maduro a usurper, and call for the establishment of a transitional government.”

ABC News' Meredith McGraw contributed to this report.