Sires, who spent the first 11 years of his life in the town of Bejucal near Havana, tells them how, after Fidel Castro took over, English-language books were burned and he was forced to march in parades toting a Czech-made submachine gun.

Sires' pitch is growing all the more important as opponents of U.S. sanctions on Cuba are stepping up their efforts to ease them, hoping that with Fidel Castro ailing and Democrats running Congress, their chances of victory will improve.

Keep the sanctions in place until the Castro government makes significant political and human-rights reforms, Sires tells his fellow Congress members.

The 56-year-old lawmaker says he has made this pitch to most of the 55-member freshman legislative class, underscoring the kind of determined lobbying by Cuban-American legislators and allies that have made them confident they can beat back critics of U.S. policy toward Cuba.

Sires is the new kid on the block, a first-time lawmaker joining more seasoned veterans of Cuba-policy battles -- Miami Republican Reps. Ileana Ros-Lehtinen and Mario and Lincoln Díaz-Balart and Democratic Rep. Debbie Wasserman Schultz of Pembroke Pines -- in leading a campaign in the House to stay the course on Havana.

Mel Martinez, R-Fla., and Bob Menendez, D-N.J., are carrying the load in the Senate. Sires holds the House seat once held by Menendez.

Sires and Wasserman Schultz, together with other pro-sanctions legislators, have drawn up lists of lawmakers and their positions on Cuba. Those who are new to the issue or undecided get a full briefing, with Sires focusing on the freshmen. Others who have voted against easing sanctions in the past are pulled aside for a brief chat to make sure their position hasn't changed.

Sires and Wasserman Schultz belong to the Cuba Democracy Caucus, created in 2004, which brings together 18 House members and seven senators, with more expected to join in the coming weeks, Wasserman Schultz says.

Caucus members say the group is more active than ever, sending out letters to colleagues, explaining their positions on Cuba.

Wasserman Schultz and other caucus members believe that they can win the legislative battles this year, but they recognize that the fight will not be easy.

The office of Rep. Lincoln Díaz-Balart counts six Cuba-related bills filed since January, including proposals that would lift restrictions on Cuban-American travel to the island and facilitate agricultural exports. One initiative that would lift a ban on U.S. tourist visits to Cuba got more than 70 co-sponsors.

Mavis Anderson, with the Latin America Working Group, an advocacy organization that pushes for more engagement with Cuba, says supporters of a tough position on Cuba have lobbied aggressively, but she believes that the tide is shifting.

''I don't think they can roll over the majority, which really sees the ineffectiveness and incorrectness of this policy,'' she said.

Supporters and opponents of U.S. policy on Cuba say that repealing restrictions on Cuban-American travel, widely criticized as separating families, stands the best chance of succeeding.

''Opponents are doing their best to pull the heartstrings of members,'' said Wasserman Schultz. While sharing those concerns, she said, ``we try to explain the complexity of the issue. . . . For most of my colleagues, it requires an education.''

Supporters of sanctions say a policy change now would let Fidel's brother Raúl Castro consolidate his hold on the government and remove any incentive to make changes.

Mauricio Claver-Carone, the Washington director of the U.S.-Cuba Democracy Political Action Committee, which lobbies to keep the sanctions, compares the moment with the final stretch of a marathon.

''Potentially, we have 50 yards left,'' he said of Fidel Castro's ailment. ``If you're going to change your shoes in those last 50 yards, you have to feel 150 percent sure that those shoes are not going to cramp you up.''

The pro-sanctions group is also adjusting its message to the reality of a Democratic majority in Congress, focusing on human-rights and labor abuses by the communist government.

''I think we win once we tie it to the abuse of human rights, once we tie it to the freedom to express yourself, once we call for election, for the release of political prisoners on the island,'' Sires told The Miami Herald.

Democrats have been holding up several free-trade agreements on the grounds that they don't do enough to protect the rights of foreign workers. Yet many of those Democrats also want more trade with Cuba -- an apparent contradiction alleged by Commerce Secretary Carlos Gutierrez in a recent speech.

Sires says some members of Congress are receptive to his pitch. Others from districts that have gained from trading more with Cuba express some doubts.

''Like anything else,'' Sires said, ``you just have to work it.''