By Tom Brook BBC entertainment correspondent in New York

The Sum of All Fears, the first big-budget Hollywood release since 11 September to feature a terrorist nuclear strike on US soil, arrives in UK cinemas on Friday after unnerving American audiences.

Even though the film has an eerie timely resonance, this fourth screen adaptation of a Tom Clancy bestseller, starring Ben Affleck as CIA analyst Jack Ryan, had in fact been conceived, cast and shot well before 11 September.

Scenes from the action thriller showing a nuclear device being detonated close to US city of Baltimore during the football Superbowl elicited audible gasps of horror when the film was screened in American cinemas.

For many anxious US moviegoers these vivid celluloid images of a terrorist-triggered nuclear attack on home ground, in the wake of 11 September, struck unnervingly close to home.

Morgan Freeman plays the head of the CIA

The carnage felt disturbingly real and the action scenes that followed the attack did not play as some far-fetched Hollywood fantasy.

There is no doubt that The Sum of All Fears, originally conceived as just another summer popcorn movie, came to be viewed as an entirely different film, more of a hard-hitting drama, as a result of 11 September.

For Hollywood, the strong box office performance of The Sum of All Fears, which has so far grossed more than $118m (�76m), certainly eased concerns among studio executives that audiences would be resistant to films with terrorist themes.

Provocative

Director Phil Alden Robinson says the only adjustments made to The Sum of All Fears, after 11 September, were in post-production.

Robinson says he instructed his team to ensure the portrayal of nuclear devastation in Baltimore did not include any buildings that resembled the Twin Towers of the World Trade Center.

Movie historians will probably not view this thriller as a pivotal film that captured the zeitgeist of post-11 September America

The film was marketed in the US with a campaign mindful of post-11 September sensitivities.

But with official publicity material for the movie posing the provocative question "could terrorists actually detonate a weapon of mass destruction on US soil?", there is no doubt that the studio was trying to capitalise on the heightened anxieties in the wake of the attacks.

Paramount Pictures, the studio producing The Sum of All Fears, would probably have been much more nervous over its release had the screenplay followed Tom Clancy's 1991 bestseller more closely.

In Clancy's original work the terrorists were Muslim.

But in the movie adaptation they have been changed to European neo-Nazi villains, who hope that detonating a nuclear device at the Superbowl will confuse the US and set off nuclear exchange between American and Russia that will assure their mutual destruction.

Pressure to change the identities of the terrorists came during early stages of production from the US based Council on American-Islamic Relations, who viewed Clancy's novel as a Muslim-bashing tome.

Ben Affleck: Critics have questioned his ability to carry the role

The organisation's spokesman, Ibrahim Hooper, is relieved the film's producers decided not to make the terrorists Muslim, particularly in light of the 11 September attacks.

Disturbing

"When there's enough reason for anti-Muslim hysteria we didn't need something else," he says.

"There are pressure groups that like to maintain Muslims and Arabs as the perpetual bad guys, they weren't happy when it was changed."

Although US critics found the nuclear explosion in The Sum of All Fears both disturbing and gripping, many of them did not rate the film itself that highly.

Some reviewers found holes in the storytelling.

Others debated whether Ben Affleck had sufficient weight as an actor to take over the Jack Ryan role that in previous Clancy screen adaptations had been played by both Harrison Ford and Alec Baldwin.

Movie historians will probably not view this thriller as a pivotal film that captured the zeitgeist of post-11 September America.

That will probably come from a future picture either influenced by - or made in direct response to - last year's terrorist attacks.

But The Sum of All Fears will forever stand as a curiosity piece - cinema created before 11 September, which resonated with audiences in a way the filmmakers could never have imagined.