Unease in Congress at the scope of anti-terrorism legislation being rushed through by the US Attorney General, Mr John Ashcroft, has led to the postponement for a week of voting on the issue.
Democrats and Republicans alike, backed by the American Civil Liberties Union, while supporting most of the measures, including increased sentences for terrorist-related crimes and the easing of surveillance curbs, have warned that elements of the legislation may be unconstitutional. There are specific concerns about provisions for indefinite holding of suspect immigrants and the use in US courts of evidence from wiretaps abroad. Members of Congress have sought more time to consider the measures and for talks with Mr Ashcroft.
Speaking to the House Judiciary committee on Monday Mr Ashcroft warned, however, that "the American people do not have the luxury of unlimited time in erecting the necessary defences to future acts".
But even Republicans were urging against undue haste. "Why is it necessary to rush this through?" asked Mr Robert Barr, the conservative Georgian Republican. "Does it have anything to do with the fact that the Department (of Justice) has sought many of these authorities on numerous other occasions, has been unsuccessful in obtaining them, and now seeks to take advantage of what is obviously an emergency situation?"
The administration's bill would make it easier for law enforcement agencies to eavesdrop on suspected terrorists by allowing them wiretap individuals rather than individual telephone lines, enabling them to access mobile phone communications and e-mail.
Investigators could also obtain wiretaps and electronic eavesdropping authorisation valid anywhere in the US for up to a year. They could seize unopened voice mail and e-mail messages with a search warrant and not a court order. And they could execute a search warrant without prior notification.
The Administration argues that it is only updating the law to take account of technological developments and extending to domestic investigations of terrorism powers already provided for in espionage investigations.
The legislation would also also expand the definition of terrorists to include those who "lend support" to terrorist organisations, and it would allow immigration officials to "detain and remove" them.
"Currently, for instance, harbouring persons engaged in espionage is a specific criminal offence, but harbouring terrorists is not," Mr Ashcroft said.
But Mr John Conyers, an Illionois Democrat, argued the power to detain immigrants indefinitely had already been turned down as unconstitutional by the courts. Mr Barney Franks of Massachusetts, also Democrat, expressed concern over powers being given to agencies to share information and not only freeze assets but seize them. He insisted on safeguards to ensure information gathered in this way would not be used politically against citizens, recalling the "savage campaign of defamation waged by J. Edgar Hoover as head of the FBI against Dr Martin Luther King".
Similar concerns were yesterday raised in the Senate Judiciary Committee where the chairman, Sen Patrick Leahy, a Democrat from Vermont, is understood to be concerned about detention and information-sharing provisions. The ranking minority member, Sen Orrin Hatch from Utah, yesterday insisted that the measures sought were "measured and moderate".
The concerns about the right to tap e-mails reflect an ongoing tussle between the Department and Congress. The FBI has developed a sophisticated eavesdropping technology for the task, most prominently a system code-named "Carnivore". It can be installed on the network of an internet service provider to capture e-mail messages to and from a specific account, or simply to capture routing information identifying who a user corresponds with.
Carnivore can also track all the web servers visited by a suspect. Conversely, it can track all the visitors to a particular server or website.
Civil liberties groups have argued that telephone and Internet communications should be treated differently because web site identification and the subject line of e-mails provide far more information than telephonic surveillance.
They are also unconvinced that Carnivore limits electronic surveillance to an intended target. Until the recent attacks internet service providers did not allow the FBI to install Carnivore.