A US-backed drive to deliver foreign aid to Venezuela has met strong resistance as troops loyal to President Nicolas Maduro blocked the convoys at the border.
They also fired tear gas on protesters in clashes that left two people dead and around 300 injured.
As night fell on Saturday, opposition leader Juan Guaido refrained from asking supporters to continue risking their lives trying to break through the government's barricades at the Colombian and Brazilian borders.
Instead, he said he would meet US Vice President Mike Pence on Monday in Bogota at an emergency meeting of mostly conservative Latin American governments to discuss Venezuela's crisis.
But he did make one last appeal to troops to let the aid in and urged the international community to keep "all options open" in the fight to oust Maduro given Saturday's violence.
"How many of you national guardsmen have a sick mother? How many have kids in school without food," he said, standing alongside a warehouse in the Colombian city of Cucuta where 600 tons of mostly US-supplied boxes of food and medicine have been stockpiled.
"You don't owe any obedience to a sadist who celebrates the denial of humanitarian aid the country needs."
Throughout the turbulent day on Saturday, as police and protesters squared off on two bridges connecting Venezuela to Colombia, Guaido made repeated calls for the military to join him in the fight against Maduro's "dictatorship".
Colombian authorities said more than 60 soldiers answered his call, deserting their posts in often-gripping fashion, though most were lower in rank and didn't appear to dent the higher command's continued loyalty to Maduro's socialist government.
For weeks, US President Donald Trump's administration and its regional allies have been amassing emergency food and medical supplies on three of Venezuela's borders with the aim of launching a "humanitarian avalanche".
It comes exactly one month after Guaido, in a direct challenge to Maduro's rule, declared himself interim president at an outdoor rally.
At the Simon Bolivar bridge, a group of aid volunteers in blue vests calmly walked up to a police line and shook officers' hands, appealing for them to join their fight.
But the goodwill was fleeting and a few hours later the volunteers were driven back with tear gas, triggering a stampede.
At least 60 members of security forces, most of them lower-ranked soldiers, deserted and took refuge inside Colombia, according to migration officials. One was a National Guard major. Colombian officials said 285 people were injured, most left with wounds caused by tear gas and metal pellets that Venezuelan security forces fired.
Analysts warn that there may be no clear victor and humanitarian groups have criticised the opposition as using the aid as a political weapon.
