The action against a close supporter of Cuban exile militant Luis Posada Carriles could pit the Bush administration against part of a Republican constituency.

BY OSCAR CORRAL AND JAY WEAVER

Santiago Alvarez, a longtime anti-Castro activist and key supporter of exile militant Luis Posada Carriles, was arrested in Miami this weekend on federal weapons and passport charges -- a move that could cause a clash between the Bush administration and some members of one of the president's most loyal political constituencies.

Alvarez, a wealthy developer, is charged with possession of automatic weapons, including some with the serial numbers obliterated; a silencer not properly registered; and a false passport, Matthew Dates, spokesman for the U.S. attorney's office in Miami, said Sunday evening.

Some Cuban-American activists criticized the arrest as an attempt to appease Fidel Castro at a time when the Cuban president is stepping up his rhetoric against Posada and his associates.

The U.S. government was already in the uncomfortable position of being accused of harboring Posada, who is suspected of terrorism, even as it wages a global war on terrorism. Now, Alvarez's arrest could raise the political stakes by pitting the Bush administration against some segments of the exile community, which has strongly supported the president.

Federal agents arrested Alvarez at his Belle Meade home about 1 a.m. Saturday, just hours after executing a search warrant in his Hialeah office, said Kendall Coffey, Alvarez's lawyer.

It was not clear whether the charges were directly related to Posada, who is wanted by both the Cuban and Venezuelan governments for his alleged role in the 1976 bombing of a Cuban jetliner and a string of bomb attacks in Havana in 1997-98.

REACTION TO ARREST

Alvarez's arrest shocked his friends and many in the exile community who say it was a major propaganda victory for Castro. The Cuban leader has been pressuring the U.S. government for months to take action against Alvarez and others, who Castro claims helped smuggle Posada into the country in March.

''Castro has got to be really happy about this because there was a week of rumor and speculation about his health, and the week ends up with what he will trumpet as a victory against the Miami Cuban-American community,'' Coffey said. ``Santiago Alvarez has not violated the laws of this country.''

A federal law-enforcement source said it was a ''pure coincidence'' that Alvarez's arrest occurred the day after a Cuba-based group ran a full-page ad in The New York Times denouncing Posada. The official said the timing of Alvarez's arrest had nothing to do with Castro or any pressure he was trying to exert on the U.S. government.

Coffey said he is concerned that the government will try to charge Alvarez in a court outside Miami-Dade County to help secure a more favorable jury for the government's position.

PROTEST PLANNED

At least one Cuban exile group, Vigilia Mambisa, plans to protest Alvarez's arrest outside the federal courthouse in downtown Miami, Mambisa President Miguel Saavedra said.

''Every time Castro complains about something, this government does whatever they have to so that he doesn't get mad,'' Saavedra said.

Alvarez, 64, became widely known in South Florida this year as the most outspoken supporter of Posada, who has been accused of anti-Castro terrorism around the hemisphere.

Alvarez said he helped shelter Posada in Miami until federal agents arrested him in May on charges of entering the country illegally.

In late September, a U.S. immigration judge ruled that Posada could not be deported to Cuba or Venezuela because he likely would be tortured there -- a decision that angered the governments of both nations.

The Cuban government's campaign against Alvarez goes back years. In 2000, Cuban Foreign Minister Felipe Pérez-Roque said in a televised speech that Alvarez conspired with other exiles to try to kill Castro at the Ibero-American summit in Panama City that year.

Alvarez denied the allegation.

ALLEGED PLOT

Havana also accused Alvarez of financing a botched terrorist mission to Cuba in 2001. The alleged plot failed after Cuban authorities arrested three Miami-Dade County men who were trying to land on the island with four AK-47 assault rifles, one M-3 rifle with a silencer and three Makarov pistols.

In a bizarre twist, one of the arrested men, Ihosvani Surís de la Torre, called Alvarez from prison while Cuban agents recorded the conversation. Surís said he was well and asked for instructions from Alvarez. He mentioned the popular Tropicana nightclub in Havana, implying that it might be a possible target.

''The other day, when you told me about the Tropicana, do you want me to do something there?'' Surís asked.

The man identified as Alvarez responded: ``If you want to do that, so much the better. Makes no difference to me.''

When asked about the tape earlier this year, Alvarez told The Herald that when he talked with the man, he knew that Surís was in the custody of Cuban agents at the time.

CLOSE RELATIONSHIP

Alvarez's ties to Posada run deep.

Last year, Alvarez paid for an executive jet to fly Posada from Panama to Honduras after the Panamanian president pardoned him and three other exiles who were serving sentences in connection with an alleged plot to kill Castro in 2000.

A federal source told The Herald that agents of U.S. Immigration and Customs Enforcement suspect that Alvarez recently received counterfeit Guatemalan passports, the basis for the search warrant.

Alvarez is scheduled to appear before a federal magistrate at 1:30 p.m. today.

Ever since reports surfaced that Posada had sneaked into the United States last March, Castro has repeatedly accused Alvarez of smuggling him into Miami aboard Alvarez's fishing boat, the Santrina.

Castro has cited the Santrina's voyage to the Mexican resort of Isla Mujeres, near Cancún, in mid-March, when the boat ran aground outside the harbor. Alvarez acknowledged in an interview earlier this year that he was in Isla Mujeres in mid-March, but said the trip was a maiden voyage for the overhauled boat.

''I am absolutely innocent,'' Alvarez said. ``We made contact with two or three people. I can't say that [the trip] had absolutely nothing to do with Posada because I've been in touch with him for years, but I can say that I didn't bring him. Santrina didn't bring him.''

Mexican government documents obtained by The Herald showed that the Santrina arrived at Isla Mujeres on March 15 with five passengers: Alvarez, Jose Hilario Pujol, Ruben Lopez Castro, Gilberto Abascal and Osvaldo Mitat. Pujol was listed as the captain.

The exit permit provided to the Santrina by the Mexican government, signed by port Captain José Luis Ibarra Rojo, said the group picked up no passengers while they were there.

Alvarez said the boat, which was recently docked on the Miami River, is owned by a nonprofit group that he started, Caribe Dive & Research Foundation. The purpose of the foundation, according to Alvarez, is to teach youths and recent Cuban arrivals to dive and respect marine ecology.

The boat's U.S. registration with the Department of Homeland Security says it belongs to the Caribe foundation and is used for recreation.

Pujol and Mitat also told The Herald that they did not bring Posada to Miami on the Santrina.

POSADA'S TRAVELS

Posada told The Herald earlier this year that he entered the United States in a car through the Mexican border. But on his way to the border, Posada said, a friend drove him from Guatemala into Belize and then into the Cancún area of Mexico.

That was about the same time that the Santrina was docked at Isla Mujeres. Posada declined to say whether he met Alvarez there.

Alvarez's longtime lawyer, Juan Zorrilla, said he visited Alvarez in jail Saturday.

''He feels that it's unfortunate,'' Zorrilla said. ``That Castro has initiated this.''