By Steve Holland

MIAMI (Reuters) - Republican presidential candidate John McCain criticized Democratic front-runner Barack Obama on Tuesday for saying he was willing to meet with Cuban President Raul Castro and accused him of wanting to weaken the U.S. embargo against Cuba.

Seeking to rally Florida's influential Cuban-American vote behind him, McCain vowed to maintain a strict economic embargo on Cuba until its communist government releases political prisoners, grants basic freedoms and schedules internationally monitored elections.

McCain's visit to Miami was all about appealing to Cuban-Americans, from his stop for coffee at a Little Havana cafe to his visit to a memorial for Cubans killed fighting the communist government.

Obama's willingness to hold talks with leaders of countries hostile to the United States, including Iran, Cuba and North Korea, has prompted daily attacks by McCain over foreign policy.

At a town hall meeting, a Cuban-American crowd booed Obama when McCain said that if elected in November the Illinois senator would "sit down unconditionally for a presidential meeting with Raul Castro -- an unconditional meeting."

McCain contrasted Obama's position to that of Presidents Franklin Roosevelt and Ronald Reagan, saying, "Roosevelt didn't talk with (Adolf) Hitler, Reagan didn't talk with (Soviet leader Leonid) Brezhnev or his two successors until (Mikhail) Gorbachev was ready to change his position."

Obama has presented his openness toward meeting leaders of countries hostile to the United States as an example of his status as a Washington outsider willing to consider new ways to address foreign policy problems.

He has said he would like to ease stringent U.S. restrictions to grant Cuban-Americans unrestricted rights to visit family and send remittances to the island.

COUNTER-ATTACKS

Responding to McCain in a Fox News Channel interview, Obama said he backed "tough, strong, direct diplomacy" and any talks would be preceded by preparation.

"If you keep on doing the same thing over and over again, and it doesn't work, then at some point you need to start thinking about something new," he said.

He suggested he would not necessarily meet Iranian President Mahmoud Ahmadinejad as McCain charges, saying he did not think Ahmadinejad was Iran's most powerful leader.

The Democratic National Committee said McCain has not always been so firm on Cuba.

The committee said when McCain was running for president in 2000 he promised to work toward normalizing relations with then-Cuban President Fidel Castro and offered to negotiate a free trade agreement before Cuba held free elections.

McCain told reporters his position has been consistent: Cuba must hold free elections before any normalization can take place. He said most Americans would agree with him that U.S. presidents should be careful meeting leaders of hostile countries because it could embolden their leaders.

"There's a huge difference there, and it's got to do with experience and knowledge and judgment, none of which Sen. Obama has," McCain said.

He was in Miami to mark Cuba's independence in 1902 with the Cuban-American community, although the Cuban government celebrates other dates such as the revolution on January 1, 1959.

(Editing by Patricia Zengerle)

(To read more about the U.S. political campaign, visit Reuters "Tales from the Trail: 2008" online at http://blogs.reuters.com/trail08/)