Miami ? Havana’s billboard war saw more salvos fired Tuesday as the U.S. and Cuban governments stoked their decades-old confrontation with competing messages.

Cuban leader Fidel Castro shepherded about 1 million people to a protest outside the U.S. diplomatic mission in the Cuban capital in one of his government’s periodic immense protests against Washington.

But just as the 79-year-old leader was about to speak to the masses, American diplomats couldn’t resist taking advantage of a captive audience and lit up the electronic ticker billboard recently displayed on the side of the building.

“To those who may want to be here, we respect your protest. To those who don’t want to be here, excuse the bother,” the sign declared in a subtle reference to the strong government pressures that ensure attendance at such protests is high.

The sign was the latest in a public relations battle between Cuba and the diplomatic mission, officially known as the U.S. Interests Section, each using billboards and displays to mock the other.

Cubans march past the U.S. Mission in Havana, which has a moving electronic message display along its fifth floor. Fidel Castro directed a protest march past the mission Tuesday, and U.S. officials used the opportunity to flash messages to the crowd.

“To help Cubans shuck off their propaganda straight jacket, we have creatively used new measures to dialogue with them – and the streaming, electronic billboard is just our latest initiative,” U.S. Interests Section chief Michael Parmly said in an e-mail to The Miami Herald. “Our goal is to show Cubans that other long-repressed people have realized their democratic aspirations.”

Another of the billboard’s messages Tuesday read, “Only in totalitarian societies do governments talk and talk at their people and never listen.”

Castro was clearly irked by the billboard, calling it another “provocation” aimed at forcing a total break in U.S.-Cuba relations.

“They turned on the little sign. How brave the cockroaches are,” Castro retorted. “Looks like Bushecito gave the order.”

Castro called for the “March of the People” two days ago to protest the U.S. refusal to extradite Luis Posada Carriles, a Cuban exile accused in a 1976 bombing of a Havana airliner that killed 73. Lasting seven hours and led by former Nicaraguan President Daniel Ortega, it was one of the largest such marches in recent years.

Posada was acquitted by a Venezuelan court in the Cuban airliner explosion, but escaped from prison while awaiting a government appeal. He was captured in Miami last year and is being held in Texas by an immigration court; Tuesday was the last day for evidence to be presented in his efforts to win his freedom.

Marchers were able to see the U.S. billboard messages, including the news that the U.S. Treasury Department had decided to allow Cuba to play in the upcoming World Baseball Classic tournament. They also saw quotes from Lech Walesa, Mahatma Gandhi and Abraham Lincoln.

“Only such regimes would be outraged by the sayings of Martin Luther King, Vaclav Havel and Gandhi,” Parmly said.