Robert Pattinson says he couldn't compete with Taylor Lautner's muscles while filming the new 'Twilight' movie 'Eclipse.'

The third film in the Twilight Saga, 'Eclipse' is due out next month and Pattinson, 23, admitted he couldn't match up to Lautner, 18, in the muscle stakes.

'There are a couple of scenes where we have confrontational scenes. I sort of push him around a little bit. I was supposed to grab his shoulder, and it wasn't even in the script. I thought I would really scare him and it would freak him out and turn the whole scene upside down."

Things didn't go to plan, though, due to Lautner's hulking frame.'His shoulder was too big to actually get a grip on. So he just brushed it off, so that was kind of embarrassing.'

'I got him badly, though. He kept having to dress up in a little grey Spandex wolf suit all the time and try and be intimidating with Kristen patting him on the head. That was fun to get him back.'