International pressure mounted against Venezuela's leader Nicolas Maduro on Sunday, with Washington vowing to "take action" after opposition efforts to bring humanitarian aid into the country descended into bloody chaos.
Self-declared interim president Juan Guaido called on the international community to consider "all measures to free" Venezuela after clashes at the border crossing left at least two people dead.
Guaido announced he would participate in Monday's Lima Group meeting of mostly Latin American countries in Bogota, and called on the international community to be prepared for "all possibilities" regarding Maduro. US Vice President Mike Pence will represent Washington at the meeting.
Secretary of State Mike Pompeo said the United States "will take action" as he condemned violence perpetrated by Maduro's "thugs." President Donald Trump has said that Washington is not ruling out armed action.
Humanitarian aid, much of it from the United States, has become the centerpiece of the standoff between Maduro and Guaido, the 35-year-old leader of Venezuela's National Assembly who declared himself interim president one month ago.
The country is gripped by a humanitarian crisis that has seen poverty soar during a prolonged recession and hyperinflation.
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Maduro claims the aid is a smokescreen for a US invasion, and has ordered several crossings on Venezuela's borders with Colombia and Brazil closed.
Two people, including a 14-year-old boy, were killed in clashes Saturday with Venezuelan security forces that left more than 300 people wounded at various border posts.
Guaido had set a Saturday deadline for delivering food and medical aid stockpiled in Colombia and Brazil.
Hundreds of Venezuelans, many dressed in white, were frustrated in their attempts to collect the aid at the Colombian border, where they were pinned back by Maduro's security forces.
Trucks with aid were prevented from entering the country, and force was used to keep out Venezuelan nationals trying to cross in from Colombia carrying aid parcels.
Colombia ordered aid trucks to return from the border after the violence.
International aid is also being held on the Caribbean island of Curacao.
A ship with aid from Puerto Rico was forced to turn back after receiving a "direct threat of fire" from Venezuela's military, the governor of the US territory Ricardo Rossello said. He slammed the move as "unacceptable and outrageous."
"I will never bow down, I will never give in. I will always defend our country with my own life if necessary," Maduro told a rally of his supporters in Carcas, after thousands had marched through the city under the slogan