The FBI has warned that al-Qaeda's next attack in the United States could be against a railway.
Officials said terrorists may attempt to destroy bridges, key sections of track or train engines to try to cause massive crashes.
They said the warning came from information provided by al-Qaeda's prisoners of the war on terror. The attacks may be carried out "using operatives who have a Western appearance," the FBI said.
Intelligence officials continue to believe al-Qaeda's plans to attack targets that would be readily recognised as representing US economic interests, the FBI said.
Captured photographs of US train engines, carriages and crossings have increased concern about the threat, the agents said.
The warning coincided with a report from an independent thinktank that said the United States remains "dangerously unprepared" to deal with another major terrorist attack,
In all likelihood, the next attack will result in even greater casualties and widespread disruption to American lives and the economy than the September 11th attacks, said the task force chaired by former senators Mr Gary Hart and Mr Warren Rudman.
The report claims: "There are already signs that Americans are lapsing back into complacency".
AP