More than 5,000 Cuban students have rallied outside the US mission in the capital, Havana, amid a row over US Christmas decorations.
The US says it wants to draw attention to human rights
Speakers at the protest organised by the government described US foreign policy as "fascist" and US diplomats in the capital as "subversive".
Cuba has objected to the US display, which refers to jailed dissidents, and hit back with images of abuse in Iraq.
The US says their decorations will stay in place until the end of the holidays.
US Secretary of State Colin Powell said the Cuban reaction was "unwise."
He told the Associated Press news agency that the US would "continue to stick by our troops down there, our diplomats down there and our Christmas display."
The leader of Havana University students said at Monday evening's rally:
"The new fascism of the US continues harassing our revolution.
"As long as the provocations continue, we
will do what is needed to fight them," Carlos Lage added.
The Cuban display includes a swastika
The Cuban government has warned the most senior US diplomat in the country, James Cason, that his choice of decorations will have serious consequences.
The display at the US interests section includes a huge white Santa Claus, an image of galloping reindeer and a flashing sign wishing Cubans a Happy Christmas.
A large figure 75 is picked out in neon, inside a large circle, in reference to the number of Cuban dissidents jailed last year.
After complaining to Mr Cason, Cuban officials set up a billboard including images of abused Iraqi detainees at the Abu Ghraib prison in Baghdad, and a swastika.
The US diplomat said last week that any action taken by Cuba against US personnel or the US mission in Havana would not affect his government's determination to draw attention to human rights.
Fourteen dissidents have been freed since the arrests took place in March 2003.