Venezuelan President Hugo Chavez and his counterpart Alexander Lukashenko vowed solidarity at a meeting in the Belarus capital, Minsk, on Friday.
The two leaders discussed economic ties, energy development and military projects.
Mr. Chavez said only a few countries in the world have to face such strong pressure from what he called "the empire" - referring to the United States - as do Belarus and Venezuela.
Washington has repeatedly criticized both governments for the suppression of free speech.
The Venezuelan leader arrived in Minsk from Moscow, where he urged Russian oil and gas companies to expand investment in his country's energy reserves.
He also met with members of the lower house of Russia's parliament (the State Duma), and had dinner Thursday night with President Vladimir Putin.
Russia's state arms export company, Rosoboronexport, announced that negotiations are under way for Venezuela to buy five diesel-powered submarines.
Venezuela bought three billion dollars worth of helicopters, fighter jets and other armaments from Russia last year, sparking concern in the United States.
Mr. Chavez's visit to Russia came before the Russian leader is to meet with President Bush on Sunday and Monday at the Bush family home in Kennebunkport, Maine, in the northeastern U.S.
The Venezuelan president will stop in Iran before concluding his trip.Some information for this report was provided by AFP, AP.