Actor Jake Gyllenhaal is deeply "in love" with girlfriend Reese Witherspoon, according to his producer pal Ryan Kavanaugh.

The Brokeback Mountain hunk has been romantically involved with divorced mother-of-two Witherspoon since meeting on the set of their 2007 film Rendition.

And Kavanaugh - who worked with the actor on forthcoming film Brothers - insists the Legally Blonde beauty could be 'the one' for Gyllenhaal.

He tells People.com, "I just think he loves her. (Jake) has obviously had his fair share of dating. I think eventually you come to a place where you know what you want and seeing what we saw on the set, he was certainly completely devoted to her and really loves her."

Of his friendship with Gyllenhaal, he adds, "He's a true artist and a really good guy. We used to work out every morning before going on the set, so he became a good friend too."

Witherspoon's eight year-marriage to actor Ryan Phillippe ended in 2006, and their divorce was finalised on 5 October (07). The former couple has two children together, eight-year-old Ava and four-year-old Deacon.