Unstoppable, the latest action thriller to reunite Denzel Washington and Tony Scott, may have, erm, stopped. Or at least slowed down to a crawl.

The Hollywood Reporter is reporting (naturally) that Fox is getting a little concerned about escalating budget costs on the movie, about an unlikely duo (Washington and Chris Pine) who team up to stop a runaway train, laden with toxic chemicals, from going big badda boom in a populated area.

With an autumn date pencilled in, THR is saying that the deals for Scott, Washington and Pine haven’t yet been signed and sealed. And with Washington in particular commanding a heavy salary in the $20 million region, the studio may be attempting to trim the budget somewhat; and that could be as good a place as any to start.

The reported stance is apparently one being considered by most studios in Hollywood, who see this summer as proof positive that big stars don’t necessarily open movies any more. After all, the four biggest films of the summer so far – Up, Transformers: Revenge Of The Fallen, Star Trek (which, of course, turned Pine into a star and bagged him the Unstoppable gig in the first place) and The Hangover – weren’t sold on their casts, while star-driven films like Christian Bale’s Terminator Salvation, Tom Hanks vehicle Angels & Demons and Scott/Washington’s own The Taking Of Pelham 123 have fared less well.

Of course, you could argue that those films – particularly Pelham – would really have underperformed without the likes of Washington and Hanks to attract and reassure sceptical audiences, but that appears to be the collective mindset for the time being. We’ll see how long that lasts.

The Hollywood Reporter, though, is saying that Unstoppable should still go ahead, but only after a vigorous budget once-over from Fox suits armed with calculators, abacuses and Carol Vorderman. Fingers crossed, because we’ve liked this concept and star/director team since we first heard it, and we’d hate to see it derailed this close to the start of production.