Despite having the world's largest oil reserves, Venezuela is in a historic crisis after 20 years of socialist rule launched by the late President Hugo Chavez. Dozens of political parties that make up Venezuela's opposition have failed to mount a viable political challenge. Critics accuse Maduro, Chavez's hand-picked successor, of unfairly winning an election last year for a second six-year term by banning his popular rivals from running. Some anti-Maduro leaders are jailed and others have fled Venezuela fearing for their safety. Last month, the 35-year-old Guaido was named leader of the opposition-controlled National Assembly. He's managed to rally masses of Venezuelans into the streets to show their support, and he's won backing from nearly 50 countries worldwide, including the United States. Juan Guaido at a rally this month. Credit:Bloomberg

How does aid fit in? Offers of humanitarian assistance are coming in from around the world. The Trump administration offered Guaido's interim presidency an initial $20 million in support and Guaido says the aid will come in through neighbouring Colombia, Brazil and as yet unidentified Caribbean islands. But Venezuela has refused them. On Feburary 22, Venezuelan soldiers opened fire on a group of civilians attempting to keep open a segment of the southern border with Brazil for deliveries of humanitarian aid. The violence claimed four lives as the food shipments remained blocked. Nicolas Maduro during a televised press conference in Caracas, during which he denounced the presence of trailers of humanitarian aid brought to the Colombian border. Credit:Bloomberg

What's Maduro saying? Maduro has refused the aid, disavowing any humanitarian crisis and saying Venezuela is not a country of beggars. He's offered to try to resolve the political impasse in a dialogue with opposition leaders, which critics call a stalling tactic that has failed to lead to any changes. More defiantly, the socialist President contends that the aid is part of a US-led coup against him, with a goal to colonise Venezuela and exploit its vast oil resources. The Venezuelan military has barricaded a bridge connecting the two nations with a tanker and two cargo trailers in an apparent attempt to block the aid. What's the opposition's next move? Since firing on the civilians, US Vice President Mike Pence said he would announce "concrete steps" and "clear actions" to address the Venezuela crisis when he meets on Monday with regional leaders in Bogota, Colombia, a senior US administration official said.

Washington has declined to comment on what the new measures will entail ahead of Pence's speech, to be delivered to a summit of the Lima Group after he meets with Venezuelan opposition leader Juan Guaido. Lester Toledo, an ally of Venezuelan National Assembly leader Juan Guaido, centre, speaks as US humanitarian aid is packaged at a warehouse in Cucuta. Credit:Bloomberg AP