The alleged existence of Predator bases in Pakistan was also reported in The New York Times on Feb. 22, 2008. That story mentioned "a secret CIA base in Pakistan," as well as in Pakistani media reports. In the wake of Feinstein's remarks, however, media reports about the alleged base in Pakistan have increased. One blog even published a satellite photo apparently showing Predators on the ground at what is described as an airfield inside Pakistan.

Although Feinstein's comments at the Feb. 13 hearing made no reference to either of these stories, LaVelle told reporters at the time: "We strongly object to Senator Feinstein's remarks being characterized as anything other than a reference" to the news stories.

As if to underscore the sensitivity of the entire subject, Hoekstra, the ranking Republican on the House Intelligence Committee, refused even to acknowledge the existence of the letter he and his colleagues sent objecting to Feinstein's comments. "If there was a letter like that, nobody would want to talk about it," he told NEWSWEEK. Another committee official said that he could neither confirm nor deny whether such a letter existed, but if it did, the document would be classified. Other congressional sources involved in intelligence oversight, who asked for anonymity when discussing a sensitive matter, said they were aware of the letter. Blair's office had no immediate comment.

While details of the Republicans' secret submission to Blair remain sketchy, four sources familiar with the matter said they understood that in the letter, House committee Republicans asked that the intelligence czar undertake a "damage assessment" regarding Feinstein's statements. According to the sources, one branch of the intelligence czar's office that could be asked to conduct such an inquiry would be the National Counterintelligence Executive, an obscure unit whose duties include making sure that U.S. intelligence agencies are doing enough to keep foreign spies from stealing government and industrial secrets.

Even if the intelligence czar's office agreed to conduct such an assessment, it is unclear what consequences could follow. One former government official noted that in the past, senators have been removed from the Intelligence Committee for leaking confidential material, in some cases material that was not even highly classified. However, another current government official said that to oust a senator from the committee would require evidence that any release of classified information was intentional. At the moment, said the official, there is no reason to believe that Feinstein's statements—if they contained classified information—were anything but "inadvertent."

The dispute over Feinstein's comments comes at a time when there are mounting questions about the U.S. policy of conducting the missile strikes in the first place. Indeed, some critics are likely to ask if the larger "damage assessment" question should be whether the missile strikes create more security problems inside Pakistan than they eliminate.

Last year, following increasingly dire warnings from U.S. intelligence agencies that Al Qaeda and affiliated Islamic militant groups were establishing what amounts to a "safe haven" in tribal areas on the Pakistani side of the Afghan-Pakistan border, President Bush authorized a major increase in the use of Predators against suspected jihadist targets inside Pakistan. Bush did this by changing the "rules of engagement" under which U.S. forces were allowed to fire Predator-based missiles against suspected terrorist encampments. In the years after 9/11, the administration had generally restricted Predator-based missiles to situations in which the United States had very high "confidence"—90 percent or better—from intelligence reporting that a high-level Qaeda target like Osama bin Laden was at a particular place at a particular time.