FBI agents in Miami yesterday arrested a Salvadoran businessman wanted in last January's murder of two Americans and the head of the Salvadoran land reform program, agents in the Florida city said.

FBI officials said they arrested Hans Krist, about 30 years old, at the request of the Salvadoran government, which has charged Krist in connection with the murder of Michael Hammer, 42, of Potomac, Md., and Mark Pearlman, 36, of Seattle, Washington, who were gunned down Jan. 4 while having coffee in a hotel in the Salvadoran capital San Salvador.

Hammer and Pearlman worked for the AFL-CIO's American Institute for Free Labor Development and were advisers to El Salvador's controversial land reform program. Rodolfo Vierea, 43, who was killed with the two Americans, was the leader of a peasant union and head of the land reform institute. The three were having coffee in the San Salvador Sheraton Hotel when two men shot them with automatic pistols.

Krist, born in El Salvador but holding both Salvadoran and apparently West German citizenship, is suspected of having close ties to right-wing terrorist groups bitterly opposed to the Salvadoran land reform, according to Justice Department officials.

Many landowners in El Salvador lost their estates as a result of the agrarian reform program, which is heavily backed by the U.S. government as a critical element in securing broad-based support for the civilian-military government now in power in the violence-plagued country.

The government, while engaged in a bitter struggle with leftis guerrillas, also finds itself under attack from the right over land reform and other issues, adding to a critical mix of violent incidents from all parts of the polticial spectrum.

A State Department spokesman said yesterday that officials also were investigating possible links between Krist and former major Roberto D'Aubuisson, who is close to right-wing officers in the Salvadoran Army and who is now believed to be in exile, possibly in Guatemala.

A source close to the investigation in El Salvador said in a telephone interview that the request for Krist's extradition was made last Friday, a week after Salvadoran police arrested another man in connection with the killings. Krist apparently left El Salvador just after the arrest.

U.S. officials would not say if Krist is believed to be one of the two men who actually shot the two Amercians and Viera, or if he was only allegedly involved in planning or financing the incident.

Krist was arrested at about 2 a.m. at a home in Miami Beach, according to an FBI official in Washington. A Justice Department official said it appeared that Krist was planning to leave the United States soon for West Germany or Chile.

William Doherty, executive director of the AFL-CIO program, was elated by news of the arrest and said Krist "has long been identified with the extremist right and long opposed to the land reform." Right-wing factions, Doherty said, have long sought to topple the civilian-military ruling junta, headed by President Jose Napoleon Duarte, as well as to sabotage the reform program and regain the lands taken away from them when it began in March 1980.

Doherty said the investigation was continuing but he would provide no further details.

"We don't want to jeopardize the case," he said. "We've got arrests, we want convictions. We want those guys put in jail."

Many former landowners, members of the Salvadoran oligarchy that ruled that country for decades, have settled in exile in Miami. They have been accused by Durate and some U.S. officials of funding death squads aimed at moderate and leftist reformers in El Salvador.

Officials here said there were no other persons being sought in this country by the Salvadoran government, but one well-informed source in El Salvador said the Salvadoran government may be looking for others in connection with the killings.

Krist is being held without bond in Dade County jail. A spokesman for the U.S. attorney's office in Miami said the government would oppose any bail for Krist. A bond hearing is set for Friday.

Justice Department officials said that the Salvadoran government has 60 days to produce documentation to would justify Krist's extradition to El Salvador. The final decision in the case, however, one official said, would be made by the State Department.