A senior US security official has advised Ireland and other European states to introduce the latest biometric security technologies to help protect themselves against major terrorist attacks.

He also called for more co-operation between national governments on security, and acknowledged that new security technologies could not prevent terrorist attacks against buses or trains.

In an interview with The Irish Times, James Williams, director of Visitor and Immigration Status Indicator Technology (Visit) in the US, said that new biometric security measures introduced last year in the US were now making it easier to check the identities of travellers.

He said the technology had denied entry to 700 known criminals and people who violated US visas.

In one recent case, fingerprints supplied by Interpol to the US authorities enabled a border guard to apprehend a murder suspect from Germany, he added.

He said the attacks in London last week were further evidence of the need to increase security.

Biometrics are automated methods of recognising a person from physiological characteristics, such as fingerprints, iris scanning or voice patterns.

Fingerprint scanners and crosschecks against databases of suspects were introduced last year by the US at airports and land borders to help identify any individuals who could be a threat to security.

Mr Williams, who was a lead speaker at an airport security conference in Dublin last week that was closed to the media, warned that biometric technologies are just one part of a security system required to protect against terrorism.

Intelligence is also vital, he said, as it is impossible to have biometric protection at every bus stop in a city such as London.

The US government has asked European states to embed microchips containing the biometric data of individuals in their passports to enable its border authorities to perform better identity checks on travellers.

It recently set a new target date of October 2006 for all new passports issued in visa waiver countries - such as Ireland, from where citizens do not need a visa to enter the US - to contain biometrics.

In theory, if the 27 visa waiver countries do not begin issuing new passports with the biometric chips from October 2006, citizens from these states would need to apply for a visa when they are seeking to enter the US.

The Department of Foreign Affairs recently began a procurement process to select a supplier to embed biometric chips in Irish passports.

However, this was placed on hold when the US put back the deadline for requiring biometric passports until October 2006. The deadline was previously October 2005.

Mr Williams said he was unaware that the Government had placed its procurement process on hold and urged it to move ahead with the biometrics project.

Introducing a chip containing biometric data to the passport of a traveller would make it easier for border guards to screen travellers, he said.

A new passport system was recently developed by the Government to improve the security of the document. This system has added a digital photograph to passports and could be expanded to embed a chip containing biometric data into the travel document.

This chip could be read by scanners at airports to offer guards a large image of the traveller on a computer terminal.

However, the use of this kind of biometric security technology is proving controversial in the US, where fears over costs and invasion of privacy have been aired in the media.

Last month the Visit programme was criticised for having no proposed final budget for the implementation of a biometric security system to protect the US border.

Mr Williams said he could not disclose the final budget for Visit as it was not set yet.

"We recognise these are precious taxpayers' dollars, but we believe the benefits are enormous in terms of increased security and keeping travel delays down," said Mr Williams, who points to an increase in travel since the attacks of September 11th, 2001, as proof of a renewed confidence among the travelling US public.

The US Visit programme

Most visitors to the US now experience Visit's biometric procedures - digital, inkless fingerscans and digital photograph - upon entry to the United States.

If a visitor requires a visa, the biometric and biographic information is collected at an embassy and checked against watch lists of terrorists and criminals.

Information on visitors is stored on a database, which can be cross-checked against watchlists and to ensure people do not stay in the US past their visa.

There is a 0.1 per cent "false positive" rate on biometric identifiers. This means that one out of a thousand people are inadvertently detained for secondary screening.

Biometric identifiers make it more difficult to claim someone's identity if their passport is stolen. However, they do not necessarily help in the fight against home-grown terrorists with a passport.

Visit is now testing radio frequency identification chip (RFID) technology at US land borders. This enables a speedier processing of visitors by guards.

The Irish company Daon is a supplier of technology to the Visit biometrics programme, which is estimated to cost up to $10 billion (€8.26 billion) over a decade.

Biometrics have been criticised by civil liberties groups for undermining personal privacy and there is still debate within the EU about their adoption.

The Government recently put on hold a tender to build a system to embed a microchip containing biometric data on all Irish passports. Under a new deadline it has until October 2006 to build the system or Irish citizens will need visas to enter the US.