Tim Golden

Federal investigators' discoveries in recent years of Cuban espionage activities - including an operation that penetrated the Pentagon's intelligence agency - have cast light on what officials describe as a resilient intelligence service that continues to work aggressively in the United States.

Since 1998 in Florida, the Federal Bureau of Investigation has exposed a network of at least 16 accused or convicted Cuban spies who, while often pinched for cash by their country's economic troubles, succeeded in infiltrating several Cuban exile groups and worked patiently to try to get inside American military installations.

In a separate case in Miami, a senior immigration official convicted of disclosing classified information to a Cuban agent was sentenced in June 2001, and, last September, a federal judge imposed a 25-year prison term on the Pentagon's former senior intelligence analyst on Cuba, Ana B. Montes, who admitted to long service as a Cuban spy.

The Cubans' success at stealing American secrets appears to have been mixed. But even so, these incidents, along with concerns about Cuba's possible involvement in developing biological weapons and aiding terrorists, have set off a new debate about whether Mr. Castro's Communist government remains a threat to American national security.

"These activities and others prove that they are a hostile country," Otto J. Reich, the Bush administration's special envoy for the Western Hemisphere, said of the espionage cases.

Predictably, the disagreement has set administration officials who want to step up pressure on the Castro government against bipartisan Congressional leaders who have been gaining ground in a campaign to ease restrictions on Cuba.

But the matter has also taken on new urgency since the Sept. 11 terrorist attacks. In one behind-the-scenes fight, some administration officials have sought the reassignment of one of the government's most senior intelligence analysts on Latin America, arguing, among other things, that he has been "soft" on the threats posed by Cuba, officials involved in the discussions said.

Mr. Reich, officials said, was among several foreign policy officials who complained to the White House about government intelligence assessments on Cuba, in particular the work of the analyst, Fulton T. Armstrong, the national intelligence officer for Latin America.

According to several officials, Mr. Armstrong has written skeptically about Cuba's importance as a military threat, its intention to develop offensive biological weapons and its continued inclusion on the State Department's annual list of countries that sponsor terrorism. Mr. Armstrong, a career Central Intelligence Agency analyst who now serves on the National Intelligence Council, an advisory body for the director of central intelligence, also worked on the National Security Council in the Clinton administration.

But Mr. Armstrong's supporters respond that he has been targeted by ideologues who would distort the intelligence process to get the kind of analysis they want. These officials said that while Mr. Armstrong had sometimes ruffled feathers with his outspoken style, he was widely respected as an analyst and trusted by George J. Tenet, the director of central intelligence.

Mr. Armstrong, Mr. Reich and a spokesman for the C.I.A. all declined to comment on the matter.

During the 1990's, after the demise of the Soviet bloc and

its subsidies to Cuba, a consensus emerged among American analysts that the security threat Cuba posed had greatly diminished. In 1998, a major Defense Department report to Congress concluded that the island's Communist government posed "a negligible threat to the U.S. or surrounding countries."

But that conclusion outraged Cuban-American political

leaders and some others, who insist that the Castro

government continues to threaten the United States in less conventional ways: by its alliances with countries like Libya and Iran, its support for several groups that use terrorism, and its development of biotechnology and cyberwarfare capabilities that could be used offensively. Cuban leaders deny any such threats.

More recently, some Bush administration officials have offered a new explanation for the relatively sanguine views on Cuba that emerged during the Clinton administration: subversion within the American intelligence community. "A major reason," said the undersecretary of state for arms control and international security, John R. Bolton, "is Cuba's aggressive intelligence operations against the United States."

In a speech last year, Mr. Bolton noted that one of the early drafters of the Pentagon report was Ms. Montes, the Defense Intelligence Agency analyst who pleaded guilty to spying for Cuba for 16 years. Ms. Montes was not paid to spy but said she acted to help Cuba defend itself against what she saw as Washington's hostility toward the island.

Intelligence officials said Ms. Montes gave her Cuban

handlers volumes of defense and intelligence information about Cuba, including military contingency plans, details of intelligence-gathering efforts and profiles of American officials. But while a formal assessment of the security damage that Ms. Montes caused is continuing, several officials said there was no evidence that she was instructed to shade her analysis in order to influence policy.

By contrast, the 16 Cuban spies indicted in Florida and known by their code name as La Red Avispa, or the Wasp Network, were unable to get their hands on any classified information at all. But it was not for lack of trying.

The spies operated not under diplomatic cover but as what are known as "illegals" - spies without any apparent tie to the Cuban government. They took cheap apartments, drove used cars and held their secret meetings at Burger King and Pollo Tropical, accounting to Havana for every dollar they spent.

One Cuban agent stationed on Key West persuaded his handlers to let him move in with his girlfriend, a massage therapist, after arguing that he would save on expenses. (They told him to avoid marriage and children.)

According to testimony and documents at the trial, the Cubans made mistakes. One illegal officer had to explain to Havana that his secure pager "drowned" when he left it in the pocket of his shorts and jumped into a swimming pool.

At the same time, however, their message traffic pointed to a sophisticated intelligence infrastructure behind the Miami network, one that law-enforcement officials said compensated for its poverty with meticulousness and patience.

Intelligence officials added that despite the recent blows it had suffered, Cuba's intelligence service might still have as many as a few hundred officers and agents operating in the United States.

"They are one of the most aggressive intelligence services there is," said Hector M. Pesquera, the head of the F.B.I.'s Miami office. "They made some mistakes and we were able to capitalize on them, but they are still very good. They are very determined and they work the numbers. They know we can't cover everything."

Cuba has vigorously defended five of the spies who fought and lost their cases in federal court (seven others have pleaded guilty), insisting that the men sought only to thwart terrorism by radical exiles, like a spate of Havana bombings in 1997 that killed an Italian tourist. Yet the decrypted documents also point to other, less benign pursuits.

Among the "active measures" that the spies discussed - but apparently did not carry out - were making threatening phone calls, ostensibly from radical exiles, to the publisher of The Miami Herald at the time; sending a mail bomb to a person thought to be a C.I.A. agent; and sneaking boats with explosives into Florida.

Officials said that what prompted the decision to prosecute most of the Wasp Network spies rather than simply deporting them (as is being done with the latest person accused of being a member of the network, who was arrested in May) was a link between two of the Cubans and the deaths of four exile activists whose planes were shot down by Cuban Air Force jets in 1996.