John McCain lashed out at Barack Obama Tuesday for his pledge to meet "unconditionally" with oppressive leaders, including Cuba's Raul Castro, if elected president.

"So it's dangerous. It's dangerous to American national security if you sit down and give respect and prestige to leaders of countries that are bent on your destruction or the destruction of other countries. I won't do it my friends," McCain said to a town hall-style meeting in Little Havana, the heart of Florida's Cuban-American community and stronghold of the anti-Castro movement.

Obama's plan to soften the decades-old U.S. embargo against the Cuban regime would "send the worst possible signal to Cuba's dictators," McCain said.

Cuban-American voters — who typically favor a harsh stance toward dealings with the Cuban government — make up an important voting bloc in Florida, a swing state in U.S. presidential elections.

The Arizona senator accused Obama of "shifting positions" toward the embargo — saying Obama first pledged to lift the embargo and now favors easing it.

McCain cited Obama's response to a 2003 questionnaire about his policy toward Cuba, in which the Illinois senator wrote: "I believe that normalization of relations with Cuba would help the oppressed and poverty-stricken Cuban people while setting the stage for a more democratic government once Castro inevitably leaves the scene."

Obama has said he would like to ease stringent U.S. travel restrictions toward Cuba, granting Cuban-Americans unrestricted rights to visit family and send remittances to the island.

During the Feb. 21 Democratic presidential debate at the University of Texas in Austin, Obama said, "It is important for the United States not just to talk to its friends but also to talk to its enemies. In fact, that’s where diplomacy makes the biggest difference."

He added that he would meet with Raul Castro "without preconditions," but acknowledged that there must be "preparation." The U.S. must ensure that Cuba has "an agenda" in place that addresses "human rights, releasing of political prisoners" and "opening up the press," he said.

McCain said Tuesday that his administration will oppose softening the economic embargo unless the Cuban government meets certain conditions.

"My administration will press the Cuban regime to release all political prisoners unconditionally, to legalize all political parties, labor unions and free media, and to schedule internationally monitored elections," he said.

"The embargo must stay in place until these basic elements of democratic society are met," he continued, to a standing ovation from the crowd.

During a question and answer period following McCain's speech, an audience member compared Obama to Castro. McCain responded by criticizing Obama for his willingness to negotiate with leaders like Castro and Iranian President Mahmoud Ahmadinejad.

"What are they going to talk about? The destruction of Israel?" McCain said of a possible Obama-Ahmadinejad meeting.

In an interview with FOX News on Tuesday, Obama emphasized the recent history of American presidents willing to sit down with leaders considered to be enemies of the US and of democracy. He mentioned President Reagan, who met with former Soviet President Mikhail Gorbachev and Richard Nixon, who met with Chinese Communist Party leader Mao Zedong.

"When it comes to Cuba, what I have said is we need to loosen up remittances and a travel ban for Cuban Americans to visit their families as a gesture of good faith, but the bottom line is our goal should be Cuban liberty, the same goal that I think Democrats and Republicans have, the difference is John McCain said the same thing eight years ago -- that we should look at over time, normalizing relations," he said. "He's the one who flip-flopped partly because he's pursuing the presidency."

As for Iran, Obama pointed out that "Iran is stronger now than when George Bush took office and the fact that we have not talked to them means that they have been developing nuclear weapons, funding Hamas, funding Hezbollah, we have had not impact whatsoever as we pursue our policies," he said.

He pointed out that he too, desires to see Iran "stand down on nuclear weapons," stop funding Hezbollah and Hamas, and stop threatening Israel, and those goals would be part of any future talks.

"The truth is that we don't have to worry about losing a propaganda war to dictators," he said. "We're the most powerful nation on earth, and if we're clear about what we stand for, what we advocate for, then we should not be afraid of being willing to have tough, strong, direct talks with other countries."

Meanwhile, McCain also ripped into Obama's opposition to a free trade deal with Columbia that would benefit Florida's agriculture and manufacturing industries. He called Obama "a tool of organized labor... that'd what labor unions want, no free trade agreements."

Fox News' Mosheh Oinounou and the Associated Press contributed to this report.