As the world hunkered down yesterday for fear of further terrorist attacks, Western leaders urged closer international cooperation to block any repetition of the blows that struck America on Tuesday.
But intelligence experts suggested that determined kamikazes could break through any security cordon. They wondered whether tighter links between intelligence agencies would be enough to forestall the sort of people who destroyed the World Trade Center and part of the Pentagon.
"We can only defeat this kind of terrorism by much firmer, coordinated international action," British Foreign Secretary Jack Straw said on yesterday, before flying to a meeting of European Union ministers to discuss reactions to the assault on Washington and New York.
"We are ready to cooperate with the United States in the battle against terrorism," added Javier Solana, the EU's foreign affairs and security chief. But as the full horror of Tuesday's attacks sank in, "we all know that it is impossible to be sure of stopping cells of determined terrorists who are prepared to use suicide methods," said Guillaume Dasqué, a security expert who edits Intelligence World, a Paris-based newsletter.
"In an open and democratic society, no security service can guarantee that this sort of thing will not happen," he added. In fact, cooperation between Western intelligence agencies is generally good on terrorist issues, according to people familiar with the world of espionage.
Despite traditional rivalries, "there is a camaraderie among folks who do this work," says Stanley Bedlington, a former CIA counter-intelligence agent. "Even if not on a political level, when you went down to the counter-terrorism level, there was very effective cooperation."
Some experts, however, cast doubt on the way Western intelligence services have dealt with the threat of international terrorism. Since the end of the cold war, Western spies "have been busier looking for economic secrets than for real dangers," says Christian Prouteau, a former member of the French presidential anti-terrorism unit.
At the same time, the CIA, National Security Agency, and other Western agencies have come to rely more and more on high-tech tools, such as satellites, to intercept communications. Well suited to military uses, they are of less value in tracking loose networks of terrorists around the globe.
"For that sort of job, there is only one real solution, and that is human intelligence, infiltrating the group you are interested in," said Dasquié. "And that is the hardest thing to do."
Western intelligence agencies are still struggling to come to terms with new terrorist groupings, such as Osama bin Laden's 'Al Quaeda' - self-financed, internationally organized, and independent of any particular government or state - which are especially hard to track. In the days when terrorists needed the support and protection of a government, it was relatively easy for spies to pinpoint the liaison officers in that government, and thus follow the terrorists' trail.
That is no longer the case. Mr. bin Laden enjoys apparent immunity in Afghanistan, where the Taliban authorities have refused to arrest him, but he does not appear dependent on the government in Kabul for money, or logistical support, outside the country. He arranges that himself.
He does so, however, in dozens of countries whose authorities have not always been entirely helpful to American investigators seeking the perpetrators of attacks on US targets.
The Saudi Arabian police, for example, refused to let FBI agents interrogate suspects in the 1996 bombing of an American military base in Dahran. FBI investigators in Yemen, looking into last year's suicide attack on the USS Cole, in which 16 American sailors died, complained privately of a lack of assistance from local officials. And the US National Commission on Terrorism, which reported last year, found that "Pakistan has cooperated on counterterrorism at times, but not consistently."
"This is not something that the US can respond to unilaterally," Gen. Wesley Clark, former NATO Supreme Commander in Europe told the BBC. "It needs the full and wholehearted support of its European allies, and Middle Eastern nations have to draw the line. They have to open up and work with us."