A plane intended to carry several former Latin American heads of state was not allowed to take off from Panama to Venezuela on Friday, with the presidents planning to monitor Sunday’s upcoming Venezuelan elections.

The President of Panama, Jose Raul Mulino, said that the plane was denied permission to take off due to Venezuelan airspace restrictions. The former leaders included Miguel Angel Rodriguez of Costa Rica, Jorge Quiroga of Bolivia, and Vincente Fox of Mexico, all being staunch critics of Venezuelan President Nicolás Maduro.

The former Mexican president wrote on X that the “Maduro regime can block planes, but it cannot block the hope of a determined people.”

In a press briefing, the White House stated that the US is closely observing the elections, warning Maduro of sanctions if he interferes with the process. The White House added that any political repression is unacceptable, that the candidates should peacefully accept the result, and that the process should represent the “will and aspirations of the Venezuelan people for a more democratic, stable and prosperous future.”

Maduro seeks a third term in office after years of tense relations with the US. In the past decade, millions of Venezuelans have fled their country due to economic hardship and political turmoil, with many heading to the US. Once one of Latin America’s wealthiest nations thanks to its vast petroleum reserves, Venezuela has struggled with instability driven by significant wealth inequality.