By DAVID WILLIAMS

Last updated at 23:37 03 May 2007

Britons could lose the privilege of visiting the U.S. without a visa because of fears over the terrorist threat from within the British Pakistani community.

U.S. security officials are deeply concerned at the ease with which young Britons who have trained in Pakistani terror camps can enter America under the visa-waiver programme.

Their concerns were heightened this week when five men, most of whom were Britons of Pakistani descent, were jailed for life for terrorism offences.

The leader of the terror cell, Omar Khyam, 25, had trained in Kashmir, Afghanistan and Pakistan, while two of the July 7 suicide bombers, Mohammad Sidique Khan and Shehzad Tanweer, had trained in Pakistan.

U.S. officials point out that any members of the two terror cells would have been able to enter the U.S. as holidaymakers using the visa-waiver system.

Michael Chertoff, the U.S. homeland security chief, believes it is unacceptable that Britons can enter his country without a visa while Pakistani citizens have to undergo rigorous screening to obtain one.

He is holding talks with British officials aimed at closing the "loophole".

One option on the table is to single out Britons of Pakistani descent and force them to complete a tough visa application.

The visa-waiver programme, which applies to Britain and several other countries, means Britons do not need a visa if they are travelling on a major airline or shipping line with a return ticket; are visiting for business, pleasure or in transit; do not plan to stay more than 90 days; and do not have a criminal record.

Some four million Britons visit the U.S. each year - the vast majority without visas - so Britain strongly opposes any change to the current system.

U.S. officials have repeatedly voiced their concerns that the system could be exploited by terrorists.

Among the options on the table in the talks between Britain and the U.S. was the total

scrapping of the waiver programme, the New York Times reported yesterday.

It said another option would be to single out Britons of Pakistani origin, requiring them to make visa applications for the U.S. and to declare details of visits to Pakistan. Each applicant would also have to undergo a face-to-face interview at a U.S. embassy.

British officials have told the U.S. this would lead to a bitter backlash from civil liberties campaigners.

It would also cause considerable embarrassment to Tony Blair, particularly as the majority of the British Pakistani community - which is some 800,000-strong - has traditionally voted Labour.

They have said the U.S. should simply deport Britons who fail screening once they arrive, pointing out that details of those visiting are sent in advance by airlines.

An estimated 400,000 Britons visit Pakistan each year and the U.S. accepts it is only a tiny minority such as Khyam and Khan who could pose a threat.

But that minority is enough, Mr Chertoff believes, to introduce controls to stop potential terrorists from Britain who have no criminal record. U.S. officials say at least four major terror trials are pending in the UK involving Britons of Pakistani origin who were unknown to the British authorities.

Former CIA officer Bruce Riedel told the New York Times that Khyam was the ' classic' UK-Pakistani connection that Al Qaeda had used since 9/11, adding: "His UK passport gave him international mobility."

A British Embassy official in Washington said the visa-waiver programme was valuable and London would oppose moves to scrap it. But he insisted Britain would not accept any special restrictions on British citizens of Pakistani heritage.

A State Department spokesman said the U.S. would "do what we can" to stop the visawaiver system being abused, but would not comment on whether it might be scrapped.

A British anti-terror investigator said yesterday: "We fully understand and share America's concerns.

"The potential threat is obvious and the British passport provides Al Qaeda operatives with the chance of entering into the heartland of their greatest declared enemy with relative ease. It poses a real problem."