"Now it's up to all of us to assert the truth that we all know. Time to mobilize", writes Machado on X.
The pressure has increased on Venezuela's President Nicolás Maduro in recent days, who has declared himself the winner of the presidential election despite the opposition claiming that they actually won.
According to the electoral commission, Maduro received 51 percent of the votes, a figure that is being questioned both domestically and internationally since the commission is controlled by people loyal to the president. An increasing number of world leaders are backing demands for an investigation into the election.
Maduro said on Wednesday evening that he was ready to show the voter lists, but simultaneously accused the opposition of having "blood on their hands" and blamed them for the deaths that occurred during the violent protests that erupted after the election.
They should be behind bars, he said to reporters.
At the same time, he claimed that the electoral system in the country had been hacked, and said that it was a reason why he could not publish the election results.
Brian Nichols, a senior American diplomat with a leading position in the US State Department, said at a meeting with the Pan American cooperation organization OAS that it is "obvious" that Maduro lost and that he is trying to conceal the result.