Poland has openly backed Belarus' main opposition candidate by allowing him to address the Polish parliament.
Alexander Milinkevich says his people must fight for their country
Alexander Milinkevich is the first opposition politician from Belarus to address the chamber since Alexander Lukashenko came to power in 1994.
Belarus opposition groups have chosen him to run against the president in elections in March.
He warned of protests if the polls were not fair, adding that people wanted transparent elections, not revolution.
"The people of Belarus have to fight for their independence, honour and their country... Only the openness of the Western World can help us," Mr Milinkevich told MPs.
"We will not give up our hopes and our dreams. Belarus is tired of humiliation."
Polish parliamentarians from all parties cheered his speech.
The BBC's Adam Easton in Warsaw says Poland would like the European Union to take firmer action against Mr Lukashenko, described by the United States as Europe's last dictator.
Warsaw accuses his government of violating human rights, rigging elections and suppressing the opposition. Poland's parliament speaker, Marek Jurek, said Belarussian opposition leaders should feel free to speak in Poland.
Our correspondent says that in an effort to boost free speech, the Polish government is about to set up a radio station to broadcast into the country.
Mr Lukashenko accuses Poland of interfering in its internal affairs and of trying to foster popular protest against him.