University students and citizens stand in silence during commemorative traffic blockade to a train station tragedy that killed 16 people before the first big rally this year of opponents of President Aleksandar Vucic in Belgrade, Serbia, Monday, May 18, 2026. (AP Photo/Darko Vojinovic)

A car passes by a big screen showing Serbian President Aleksandar Vucic, reading: " I am too stubborn. I am too much of a Serb. I love Serbia too much to be to the taste of the power mongers." before his opponents first big rally this year in Belgrade, Serbia, Tuesday, May 19, 2026. (AP Photo/Darko Vojinovic)

University students and citizens stand in silence during commemorative traffic blockade to a train station tragedy that killed 16 people before the first big rally this year of opponents of President Aleksandar Vucic in Belgrade, Serbia, Monday, May 18, 2026. (AP Photo/Darko Vojinovic)

City bus passes by a sign covered with stickers that read: "Students win" before the first big rally this year of opponents of President Aleksandar Vucic in Belgrade, Serbia, Monday, May 18, 2026. (AP Photo/Darko Vojinovic)

People walk by a lamppost with stickers that read: "Students win" before the first big rally this year of opponents of President Aleksandar Vucic in Belgrade, Serbia, Monday, May 18, 2026. (AP Photo/Darko Vojinovic)

Agustin Acosta holds a placard protesting former Cuban President Raul Castro as a handful of Cubans turned out to wave flags and hold signs hours after federal prosecutors announced charges against Castro in the 1996 downing of civilian planes operated by Miami-based exiles, Wednesday, May 20, 2026, in Miami. (AP Photo/Rebecca Blackwell)

Jose Miguel Hernandez, 14, right, wears handcuffs to represent freedom for political prisoners and a call to put former Cuban President Raul Castro in jail, while his mother Catalina Vasquez waves a flag depicting Cuban political prisoners atop a mountain overlooking prisons below, hours after federal prosecutors announced charges against Castro in the 1996 downing of civilian planes operated by Miami-based exiles, Wednesday, May 20, 2026, in Miami. (AP Photo/Rebecca Blackwell)

FILE - Former Cuban President Raul Castro looks at the Cuban flag during his speech at the event celebrating the 65th anniversary of the triumph of the revolution in Santiago, Cuba, Jan. 1, 2024. (AP Photo/Ismael Francisco, File)