US media groups are trying to speed up the overseas distribution of their leading television programmes to contain a rapidly-growing piracy epidemic fuelled by easy access to video from websites.

NBC Universal is planning, as part of that effort, to expand on a ground-breaking agreement it struck last year with France's TF-1 in which viewers were offered paid-for access to subtitled episodes of Heroes, one of its biggest hits, just a day after their US premiere.

Disney has a similar pact with TF-1 and another in Finland, while others are expected to follow suit.

They are also aiming for more synchronised releases in English-speaking markets so episodes make their debut in the UK, Canada and Australia within days, rather than months, of the US.

The moves are another sign of Hollywood's growing reliance on international markets when high-priced talent and lavish special effects are pushing up production costs. Some network executives estimate that foreign markets now account for up to half of some programmes' revenues.

Studios have traditionally taken months to export hit shows - in part because of the need to dub programmes into local languages and create marketing campaigns.

However, media executives are worried because many fans, unwilling to wait, are increasingly turning to YouTube and illegal file-sharing sites to watch their favourite programmes.

As a result, television now ranks as the fastest growing category of internet piracy, according to BigChampagne, a consultancy that measures online file-sharing.

Tom Toumazis, head of international distribution at Disney-ABC Television, said: "Fans have an insatiable appetite for seeing these shows as quickly as they can".

He said that distributing programmes more quickly was not only a way to prevent piracy but also provided a competitive advantage over other suppliers.

Over the past year, Disney has succeeded in delivering hit shows such as Lost to English-speaking countries within 24 hours while shaving two months from its dubbing process. "You're going to see a further collapse of those windows," Mr Toumazis predicted.

Belinda Melendez, president of international television distribution at NBC Universal, said the company hatched the TF-1 deal to give French fans greater chance to watch Heroes after discovering that illegal downloads of the show were twice the levels seen in the US.

At CBS, one executive said quicker releases also allowed networks to capitalise as the marketing buzz generated in the US increasingly spilled over to other audiences.