Tensions are high along the border between Colombia and Venezuela, as a major push to deliver humanitarian aid could descend into violence on Saturday.

On Friday, musicians held a Live Aid Venezuela concert in border town Cucuta, Colombia to pressure Venezuelan leader Nicolas Maduro to let humanitarian aid into Venezuela, ending the show with a rendition of John Lennon’s “Imagine.”

Concert organizer Richard Branson also took the concert stage, exhorting the crowd in a chant of “Freedom” while pumping fists. The Venezuelan government was not pleased, blocking viewers in the country from watching the concert online and on certain television outlets.

Branson said he was aiming to raise about $100 million to buy food and medicine for Venezuela. More than 30 artists participated in the event, including Colombians Carlos Vives, Juanes and reggaetón singer Maluma, Swedish DJ Alesso, Mexican rock band Mana, and singer and songwriter Alejandro Sanz.

Venezuelan opposition leader Juan Guaido also attended the concert, even though he was under orders from Maduro not to travel outside the country. He was joined by thousands of Venezuelans who have descended on the border in response to the lack of food and chaos in their country.

Saturday has been set as a deadline by Guaido to bring emergency food and medicine into the country. President Maduro has claimed the aid isn’t needed and had vowed to block any attempts to enter his country with it, sparking fears of potential violence.