A U.S. grand jury investigating an alleged plot to kill Cuban President Fidel Castro has subpoenaed the president of the Cuban American National Foundation (CANF), plus a second foundation leader and a third man to testify in the case, a lawyer for one of the men said Tuesday.

Foundation President Francisco ``Pepe'' Hernandez appeared before the grand jury in Puerto Rico on Nov. 19, but the summons for Jose Antonio Llama, a member of CANF's executive committee, was postponed, a lawyer for Llama said. The third man was not identified.

The grand jury began hearing testimony on a possible plot to kill Castro after four Cuban exiles were arrested Oct. 27 aboard a 46-foot Miami-based yacht carrying two powerful .50-caliber sniper rifles.

One of the four blurted out during an interrogation that the two rifles found in the yacht La Esperanza were meant for an attempt on Castro during a summit on the Venezuelan island of Margarita, according to U.S. Coast Guard officials.

The four were first charged only with failing to report the guns. But the FBI bureau in Puerto Rico told reporters Nov. 10 that it would continue investigating the assassination allegation through a federal grand jury in Puerto Rico.

Hernandez and Llama did not answer several telephone calls from The Herald. Foundation spokeswoman Ninoska Perez said Hernandez would have no comment on the case.

Jose A. Pagan, a lawyer in Puerto Rico retained by Llama, told The Herald on Tuesday that the grand jury had subpoenaed Llama and Hernandez to testify Nov. 19. But prosecutors later postponed Llama's testimony for unknown reasons, Pagan added.

Llama is listed in Florida as owner of the La Esperanza. It was not clear why Hernandez was subpoenaed to testify, Pagan said. The lawyer said he did not know anything about the third man subpoenaed or whether he had testified.

Pagan said he would advise Llama to take advantage of his Fifth Amendment right not to incriminate himself.

``We're not clear on what the prosecutors want,'' Pagan said in a telephone interview.

Although Cuban officials have repeatedly accused the foundation and its members of financing armed attacks on the Castro government, CANF has steadfastly denied any role in such violence.

The foundation issued a statement Aug. 13 endorsing a string of bombing attempts that racked Cuban tourism centers during the summer as a legitimate attempt to topple Castro. One Salvadoran has been charged with six of the blasts. The Herald has revealed that he was part of a criminal ring paid by Cuban exiles in El Salvador and Miami to carry out the bombings.

Hernandez, 61, who has owned an agri-business firm with operations from the Dominican Republic to Kenya, has long been president of CANF. As top executive officer, he devotes most of his time to the anti-Castro lobby.

Llama, 66, who exports auto air-conditioning systems, sits on the foundation's 28-member executive committee.

The four exiles arrested in Puerto Rico -- and now free on bond while awaiting trial on the gun charges -- are Angel Alfonso, 57, manager of a textile firm in Union City, N.J.; Angel Hernandez Rojo, 64, a Miami lumber dealer; Francisco Cordova, 50, a Marathon Key fisherman; and Juan Bautista Marquez, 61, of Miami, a former merchant seaman.

    Herald staff writer Pablo Alfonso contributed to this report.