Saturday saw deadly confrontations at border crossings as volunteers attempted to collect aid lead by Mr. Guaido
Deadly clashes broke out in Venezuelan border towns on Saturday, as President Nicolás Maduro blocked humanitarian aid from crossing from Colombia and Brazil.
At least two people were killed by gunfire on Saturday, rights groups said, including a 14-year-old boy.
Venezuelan troops fired tear gas and rubber bullets at protesters attempting to collect and transport the aid.
The opposition wants the aid to go to people hit by the economic crisis. Mr Maduro claims it is a security threat.
US Secretary of State Mike Pompeo condemned the attacks on civilians, which he blamed on “Maduro’s thugs”.
“Our deepest sympathies to the families of those who have died due to these criminal acts. We join their demand for justice,” he said in a tweet following the clashes.
Mr Pompeo also described the burning of some of the aid as “sickening”.
Media captionThe moment Venezuelan troops crashed through border into Colombia
Opposition leader Juan Guaidó, who has declared himself interim president and helped to organise the aid, condemned the action by security forces.
Mr Guaidó, who has been recognised as leader by dozens of nations, will meet US Vice President Mike Pence on Monday in Bogota, Colombia.
He is attending a meeting of the regional Lima Group, in spite of a travel ban imposed on him by Mr Maduro’s government.
On Saturday evening, Mr Guaidó posted a tweet (in Spanish) which implored the international community to be “open to all options” in order to “liberate” Venezuela from Mr Maduro – who is continuing to resist all calls to stand down.