A tense calm returned to Venezuela's borders with Brazil and Colombia on Sunday as domestic and international pressure mounted on President Nicolas Maduro.
Washington vowed to take action after opposition efforts to bring in humanitarian aid descended into chaos and violence.
Self-declared interim president, Juan Guaido, has called on the international community to consider "all measures to free" Venezuela after clashes at the border crossing left at least two people dead.
Maduro refused to allow aid to come into the crisis-hit country, resulting in violent clashes with the security forces and accusations that armed civilian groups loyal to Maduro opened fire on the crowds.
Protesters in the border towns of Urena and San Antonio were kept at bay by the Venezuelan National Guard firing tear gas and rubber bullets.
"They are shooting this and bigger iron projectiles, of this size," said one demonstrator. "This is the smallest I've seen. However, they did not shoot bullets, bullets, only because this is the Colombian side. "
"We have to go to the streets to fight for Venezuela," said another man. "Enough is enough with this tyranny. This injustice. We must help the people. Is this helping the people? It is not. This is intimidating the people".
Maduro claims the U.S. aid is a smokescreen ahead of an invasion.
But Secretary of State Mike Pompeo says he is confident "Maduro's days are numbered," and he blames the border violence on armed loyalists known as "colectivos."
Juan 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. U.S. Vice President Mike Pence will represent Washington at the meeting.
As many as 300,000 Venezuelans face death if aid isn't delivered after years of shortages and malnutrition, according to Guaido, who has accused Maduro of rigging his re-election and is demanding a new vote.
United Nations figures show that 2.7 million people have fled Venezuela since 2015 and around 5,000 Venezuelans emigrate each day.