WASHINGTON -- The deadly Tokyo subway attack shows that officials around the globe are ill-prepared to protect the public from malicious uses of a huge range of lethal modern technologies -- an especially frightening prospect in light of the apparent quantum, tactical leap taken by whoever released nerve gas in Japan's transit system, experts said.


Although no individual or group has claimed responsibility in the Japanese incident, U.S. experts said Monday it has sweeping implications for the United States and other open societies: Those responsible for the Tokyo attack have planted an idea and provided a map for others, including terrorists, to use poison gas against a civilian population.


And there now may be no way to put that ghastly genie back in the bottle.


"We've definitely crossed a threshold,'' said Bruce Hoffman, a specialist at the Center for the Study of Terrorism and Political Violence at St. Andrew's University in Scotland. "This is the cutting edge of high-tech terrorism for the year 2000 and beyond.


"It's the nightmare scenario that people have quietly talked about for years coming true,'' he said.


The Tokyo disaster suggests that an individual or a group managed not only to produce toxins but also to create systems to deliver them -- a step that is actually the more difficult of the two, said Michael Moodie of the Chemical and Biological Arms Control Institute.


In a report little noticed until now, the institute investigated a similar attack in June in the central Japanese city of Matsumoto that killed seven and sent more than 200 to hospitals after the nerve agent sarin penetrated several homes and apartments.


Weeks before the subway disaster, the institute concluded that Matsumoto was a trial run to test a delivery system for the deadly poison.


Based on preliminary evidence, U.S. officials believe that the gas used in the Tokyo attack was a home-made version of sarin or a weaker nerve agent. The industrial version of sarin would have resulted in far more deaths.


In the Matsumoto attack, other gases were mixed with sarin, Moodie said.


Sarin, experts said, can be made with common industrial chemicals used in the production, for example, of ink for ball-point pens and fertilizers. The knowledge needed is not deep; someone with a college science degree could do it.


Developing delivery systems is more difficult. Sarin, for example, is said to be highly corrosive. It would be dangerous for an extremist to handle and plant -- a key reason why it has not been used more often. At room temperature, sarin would be in liquid form. To disperse through the air, it must be a gas.


Officials in Tokyo are still investigating how it was spread through subways there. But the poison is believed to have leaked out of broken bottles and boxes wrapped in newspapers left inside five trains and at one station.


Because of the relative simplicity of their production, U.S. officials now fear that the use of chemical weapons may be copied by extremist groups, organized crime or even oddballs seeking attention. This has been a common pattern after other terrorist tactics.


The potential impact could be acute because virtually no Western country has contingency plans to deal with such an attack. "Contingency plans to deal with chemical or biological terrorism are woefully lacking,'' said Vince Canistraro, a counterterrorism expert.